像计算机科学家一样思考：用 Python 学习 第 2 版/解决方案
以下部分包含本书练习的答案。
练习 1
print("5 ** 5 is", 5**2)
print("9 * 5 is", 9 * 5)
print("15 / 12 is", 15 / 12)
print("12 / 15 is", 12 / 15)
print("15 // 12 is", 15 // 12)
print("12 // 15 is", 12 // 15)
print("5 % 2 is", 5 % 2)
print("9 % 5 is", 9 % 5)
print("15 % 12 is", 15 % 12)
print("12 % 15 is", 12 % 15)
print("6 % 6 is", 6 % 6)
print("0 % 7 is", 0 % 7)
练习 2
time_start=14 # Use 24 hour clock. Makes life a lot easier.
wait=51
time_hours= time_start + wait
days=time_hours//24
clock=time_hours-(days*24)
print("The alarm goes of at", str(clock)+":00")
练习 3
# 24 hour clock
t1=input("Enter the current time's hour using 24 hour clock: ")
t1=int(t1)
wait=input("Enter wait in hours for next alarm: ")
wait=int(wait)
t2_hrs=wait+t1
days=t2_hrs//24
t2_time=t2_hrs-(days*24)
print("The alarm goes of at", str(t2_time)+":00")
def main()
nowtime = int(raw_input("what time now: "))
t = int(raw_input("Input the hour go off your wanted: "))
time = t + nowtime
days = time//24
hour = time % 24
print "The hour will go off after days: ", days, " at hour: ", hour
pass
if __name__ == '__main__'
main()
解决方案 4 def cat_n_times(s, n)
string=s print string*n
def dispatch(choice):
if choice == 'a':
function_a()
elif choice == 'b':
function_b()
elif choice == 'c':
function_c()
else:
print "Invalid choice."
def function_a():
print "function_a was called ..."
def function_b():
print "function_b was called ..."
def function_c():
print "function_c was called ..."
choice = raw_input ("Please Enter a Function.") #had to ask about this, choice is raw input.
print dispatch(choice)
def is_divisible_by_3(x):
if x % 3 == 0:
print x, "This number is divisible by three."
else:
print x, "This number is not divisible by three."
x = input ("Enter a number")
print is_divisible_by_3(x)
def is_divisible_by_5(y):
if y % 5 == 0:
print y, "This number is divisible by five."
else:
print y, "This number is not divisible by five."
y = input ("Enter a number")
print is_divisible_by_5(y)
def is_divisible_by_n(c,z):
if c % z == 0:
print "Yes", c, "divisible by", z
else:
print "No", c, "is not divisible by", z
c = input ("Enter number")
z = input ("Enter another number")
print is_divisible_by_n(c,z)
def compare(a, b):
"""
>>> compare(5, 4)
1
>>> compare(7, 7)
0
>>> compare(2, 3)
-1
>>> compare(42, 1)
1
"""
if a > b:
return 1
elif a == b:
return 0
elif a < b:
return -1
if __name__ == '__main__':
import doctest
doctest.testmod()
def hypotenuse(a, b):
"""
>>> hypotenuse(3, 4)
5.0
>>> hypotenuse(12, 5)
13.0
>>> hypotenuse(7, 24)
25.0
>>> hypotenuse(9, 12)
15.0
"""
import math
return math.sqrt(a**2 + b**2)
# You could also use
# return (a**2 + b**2)**0,5
if __name__ == '__main__':
import doctest
doctest.testmod()
def slope(x1, y1, x2, y2):
"""
>>> slope(5, 3, 4, 2)
1.0
>>> slope(1, 2, 3, 2)
0.0
>>> slope(1, 2, 3, 3)
0.5
>>> slope(2, 4, 1, 2)
2.0
"""
return float(y2 - y1)/(x2 - x1)
if __name__ == '__main__':
import doctest
doctest.testmod()
def slope(x1, y1, x2, y2):
return float(y2 - y1)/(x2 - x1)
def intercept(x1, y1, x2, y2):
"""
>>> intercept(1, 6, 3, 12)
3.0
>>> intercept(6, 1, 1, 6)
7.0
>>> intercept(4, 6, 12, 8)
5.0
"""
m = slope(x1, y1, x2, y2)
return float(y1 - m*x1)
if __name__ == '__main__':
import doctest
doctest.testmod()
def is_even(n):
"""
>>> is_even(2)
True
>>> is_even(3)
False
>>> is_even(7)
False
>>> is_even(10)
True
"""
# You could also type just
# return n % 2 == 0
if n % 2 == 0:
return True
else:
return False
if __name__ == '__main__':
import doctest
doctest.testmod()
def is_odd(n):
"""
>>> is_odd(2)
False
>>> is_odd(3)
True
>>> is_odd(7)
True
>>> is_odd(10)
False
"""
if n % 2 != 0:
return True
else:
return False
if __name__ == '__main__':
import doctest
doctest.testmod()
def is_even(n):
if n % 2 == 0:
return True
else:
return False
def is_odd(n):
"""
>>> is_odd(2)
False
>>> is_odd(3)
True
>>> is_odd(7)
True
>>> is_odd(10)
False
"""
if is_even(n) is True:
return False
else:
return True
if __name__ == '__main__':
import doctest
doctest.testmod()
def is_factor(f, n):
"""
>>> is_factor(3, 12)
True
>>> is_factor(5, 12)
False
>>> is_factor(7, 14)
True
>>> is_factor(2, 14)
True
>>> is_factor(7, 15)
False
"""
if n % f == 0:
return True
else:
return False
if __name__ == '__main__':
import doctest
doctest.testmod()
def is_multiple(m, n):
"""
>>> is_multiple(12, 3)
True
>>> is_multiple(12, 4)
True
>>> is_multiple(12, 5)
False
>>> is_multiple(12, 6)
True
>>> is_multiple(12, 7)
False
"""
if m % n == 0:
return True
else:
return False
if __name__ == '__main__':
import doctest
doctest.testmod()
def f2c(t):
"""
>>> f2c(212)
100
>>> f2c(32)
0
>>> f2c(-40)
-40
>>> f2c(36)
2
>>> f2c(37)
3
>>> f2c(38)
3
>>> f2c(39)
4
"""
return int(round((t - 32.0) * 5.0/9))
if __name__ == '__main__':
import doctest
doctest.testmod()
def c2f(t):
"""
>>> c2f(0)
32
>>> c2f(100)
212
>>> c2f(-40)
-40
>>> c2f(12)
54
>>> c2f(18)
64
>>> c2f(-48)
-54
"""
return int(round((t * 9.0/5) + 32.0))
if __name__ == '__main__':
import doctest
doctest.testmod()
$ cat ch0601.py
print '产生', '\n', '这个', '\n', '输出'
$ python ch0601.py
产生
这个
输出
$ cat ch0602.py
def sqrt(n)
approx = n/2.0
better = (approx + n/approx)/2.0
while better != approx:
print better
approx = better
better = (approx + n/approx)/2.0
return approx
print sqrt(25)
$ python ch0602.py
7.25 5.34913793103 5.01139410653 5.00001295305 5.00000000002 5.0
def print_multiples(n, high)
i = 1
while i <= high:
print n*i, '\t',
i += 1
print
def print_mult_table(high)
i = 1
while i <= high:
print_multiples(i, high)
i += 1
if __name__ == "__main__"
high = input("Enter a number : ")
print_mult_table(high)
def print_triangular_numbers(x):
i = 1
while i <= x:
print i, '\t', i*(i+1)/2
i += 1
def is_prime(n):
"""
>>> is_prime(2)
True
>>> is_prime(3)
True
>>> is_prime(4)
False
>>> is_prime(41)
True
>>> is_prime(42)
False
"""
count = 2
#so counting starts at 2
#as all numbers can be divided by 1 and remainder = 0; and because nothing can be divided by 0
while count <= n:
if n % count == 0 and count != n:
#if when n divided by count remainder is 0
#for example when 4 is divided by 2
#and to make sure count != n because any number divided by itself then remainder = 0;
#then return False
return False
#if above is not applicable then return true for doctest to pass
elif count == n:
return True
#to make sure it doesnt exit after one try, and it counts
elif n % count != 0:
count = count + 1
if __name__ == '__main__':
import doctest
doctest.testmod()
def is_prime(n):
"""
>>> is_prime(2)
True
>>> is_prime(3)
True
>>> is_prime(4)
False
>>> is_prime(41)
True
>>> is_prime(42)
False
"""
count = 2
while count <= n:
if n % count == 0 and count != n:
return False
else:
count = count + 1
return True
if __name__ == '__main__':
import doctest
doctest.testmod()
num_digits(0) 将返回什么？
def num_digits(n):
"""
>>> num_digits(12345)
5
>>> num_digits(0)
1
>>> num_digits(-12345)
5
"""
count = 0
while n != 0:
count = count + 1
n = n / 10
return count
#num_digits(0) returns 0 because the while statement is not run,
#and therefore it returns count.
修改它，使其在这种情况下返回 1。
def num_digits(n):
"""
>>> num_digits(12345)
5
>>> num_digits(0)
1
>>> num_digits(-12345)
5
"""
if n == 0:
return 1
#the program checks if n == 0. if it's 0, it simply returns 1.
#if not, count below is initialized, then, after the calculation,
#count is returned with the final result
count = 0
while n != 0:
count = count + 1
n = n / 10
return count
为什么调用 num_digits(-24) 会导致无限循环（提示：-1/10 等于 -1）？
>>> -24/10
-3
>>> -3/10
-1
>>> -1/10
-1
>>>
当 n = 0 时，循环将结束，根据上面的提示，-1/10 == -1，导致无限循环。
def num_digits(n):
"""
>>> num_digits(12345)
5
>>> num_digits(0)
1
>>> num_digits(-12345)
5
"""
# >>> num_digits(-100) #The code must be checked with this value for assurance
# 3
# >>> num_digits(-9999) #The code must be checked with this value for assurance
# 4
count = 0
if n == 0:
return 1
elif n < 0:
n = -n
while n:
count = count + 1
n = n/10
return count
else:
while n:
count = count + 1
n = n/10
return count
if __name__ == '__main__':
import doctest
doctest.testmod()
def num_even_digits(n):
"""
>>> num_even_digits(123456)
3
>>> num_even_digits(2468)
4
>>> num_even_digits(1357)
0
>>> num_even_digits(2)
1
>>> num_even_digits(20)
2
"""
count = 0
while n != 0:
digit = n % 2
if digit == 0:
count = count + 1
n = n / 10
return count
if __name__ == '__main__':
import doctest
doctest.testmod()
def print_digits(n):
"""
>>> print_digits(13789)
9 8 7 3 1
>>> print_digits(39874613)
3 1 6 4 7 8 9 3
>>> print_digits(213141)
1 4 1 3 1 2
"""
def print_digits(n):
new = []
index = ' '
number = str(n)
for char in reversed(number):
new.append(char)
for w in new:
index = index + w
return int(index)
if __name__ == '__main__':
import doctest
doctest.testmod()
def sum_of_squares_of_digits(n):
"""
>>> sum_of_squares_of_digits(1)
1
>>> sum_of_squares_of_digits(9)
81
>>> sum_of_squares_of_digits(11)
2
>>> sum_of_squares_of_digits(121)
6
>>> sum_of_squares_of_digits(987)
194
"""
sumof = 0
while n != 0:
sumof += (n % 10)**2
n = n/10
return sumof
if __name__ == '__main__':
import doctest
doctest.testmod()
修改
prefixes = "JKLMNOPQ"
suffix = "ack"
for letter in prefixes:
print letter + suffix
以便 Ouack 和 Quack 的拼写正确。
注意，for letter in prefixes: 是遍历的替代，例如
index = 0
while index < len(fruit):
letter = fruit[index]
print letter
index += 1
#fruit = "banana"
#while index is less than 6.
#6 is the length of fruit
#letter = fruit[index]
#Since index = 0, "b" is equal to letter in loop 1
#letter is printed
#1 is added to whatever the value of index is
#the loop continues until index < 6
被替换为
for char in fruit:
print char
prefixes = "JKLMNOPQ"
suffix = "ack"
for letter in prefixes:
if letter == "O" or letter == "Q":
print letter + "u" + suffix
else:
print letter + suffix
prefixes = "JKLMNOPQ"
suffix = "ack"
for letter in prefixes:
if letter in "OQ":
print letter + "u" + suffix
else:
print letter + suffix
封装
fruit = "banana"
count = 0
for char in fruit:
if char == 'a':
count += 1
print count
在一个名为 count_letters 的函数中，并将其泛化，使其接受字符串和字母作为参数。
def count_letters(strng, letter):
\
=== CH 7 - Question 3===
Now rewrite the count_letters function so that instead of traversing the string, it repeatedly calls find (the version from Optional parameters), with the optional third parameter to locate new occurences of the letter being counted.
=== CH 7 - Solution 3===
<syntaxhighlight lang="python">
def find(strng, ch, start=0):
index = start
while index < len(strng):
if strng[index] == ch:
return index
index += 1
return -1
#for example strng = "banana"
#letter = "a"
#x = find(strng, letter, start) will return 1
#we need to modify count_letters so it returns 3
#the start variable can thus be used to our advantage
#the loop will end at the last letter of the string by returning -1
def count_letters(strng, letter, start=0):
count = 0
x = find(strng, letter, start)
while x != -1:
count += 1
x = find(strng, letter, x + 1)
return count
跟踪程序
#in our traceback, x = 1
#x = find(strng, letter, 2)
#x above will be assigned new value find(strng, letter, 2)
>>> find("banana", "a", 1)
1
>>> find("banana", "a", 2)
3
>>> find("banana", "a", 4)
5
>>> find("banana", "a", 6)
-1
>>>
关于 is_lower 的版本
def is_lower(ch):
return string.find(string.lowercase, ch) != -1
def is_lower(ch):
return ch in string.lowercase
- 这是最快的！
def is_lower(ch):
return 'a' <= ch <= 'z'
创建一个名为 stringtools.py 的文件，并将以下内容放入其中
def reverse(s):
"""
>>> reverse('happy')
'yppah'
>>> reverse('Python')
'nohtyP'
>>> reverse("")
''
>>> reverse("P")
'P'
"""
if __name__ == '__main__':
import doctest
doctest.testmod()
在 reverse 中添加函数体，使 doctests 通过。
def reverse(s):
"""
>>> reverse('happy')
'yppah'
>>> reverse('Python')
'nohtyP'
>>> reverse("")
''
>>> reverse("P")
'P'
"""
#we need to use len(s) to make it output letters
#length = len(happy) = 6
#print last = happy[length - 1] will return y
#we need to make it such that [length - 2] and so on
#we need the while loop to stop when length - x = 0
#if len(s) is 6
x = 1
while x <= len(s):
length = len(s)
lastoutput = s[length - x]
print lastoutput,
x += 1
#Why is x <= len(s)?
#because if x < len(s):
>>> reverse("happy")
y p p a
>>>
#with x<= len(s)
>>> reverse("happy")
y p p a h
>>>
现在为了使 doctest 通过，我们需要将我们的输出包含在字符串中。这里我们使用一个占位符字符串：lastoutput = ""。
其次，我们删除冗余代码
x = 1
while x <= len(s):
length = len(s)
lastoutput = s[length - x]
根据
length = len(fruit)
last = fruit[length-1]
使用负索引，例如
fruit[-1]
and
fruit[-2]
到
x = 1
while x <= len(s):
lastoutput = s[-x]
def reverse(s):
"""
>>> reverse('happy')
'yppah'
>>> reverse('Python')
'nohtyP'
>>> reverse("")
''
>>> reverse("P")
'P'
"""
last = ""
x = 1
while x <= len(s):
lastoutput = s[-x]
last += lastoutput
x += 1
return last
if __name__ == '__main__':
import doctest
doctest.testmod()
def reverse(s):
last = ""
x = 1
while x <= len(s):
lastoutput = s[-x]
last += lastoutput
x += 1
return last
def mirror(s):
"""
>>> mirror("good")
'gooddoog'
>>> mirror("yes")
'yessey'
>>> mirror('Python')
'PythonnohtyP'
>>> mirror("")
''
>>> mirror("a")
'aa'
"""
#we will be calling function reverse
#first we need it to ouput everything
s_back = reverse(s)
return s + s_back
if __name__ == '__main__':
import doctest
doctest.testmod()
def reverse(s):
last = ""
x = 1
while x <= len(s):
lastoutput = s[-x]
last += lastoutput
x += 1
return last
def mirror(s):
out = reverse(s)
out2 = reverse(out)
return out2 + out
def remove_letter(letter, strng):
"""
>>> remove_letter('a', 'apple')
'pple'
>>> remove_letter('a', 'banana')
'bnn'
>>> remove_letter('z', 'banana')
'banana'
>>> remove_letter('i', 'Mississippi')
'Msssspp'
"""
without_letter = ""
for c in strng:
if c not in letter:
without_letter += c
return without_letter
if __name__ == '__main__':
import doctest
doctest.testmod()
def reverse(s):
"""
>>> reverse('happy')
'yppah'
>>> reverse('Python')
'nohtyP'
>>> reverse("")
''
>>> reverse("P")
'P'
"""
last = ""
x = 1
while x <= len(s):
lastoutput = s[-x]
last += lastoutput
x += 1
return last
def mirror(s):
"""
>>> mirror("good")
'gooddoog'
>>> mirror("yes")
'yessey'
>>> mirror('Python')
'PythonnohtyP'
>>> mirror("")
''
>>> mirror("a")
'aa'
"""
out = reverse(s)
out2 = reverse(out)
return out2 + out
def remove_letter(letter, strng):
"""
>>> remove_letter('a', 'apple')
'pple'
>>> remove_letter('a', 'banana')
'bnn'
>>> remove_letter('z', 'banana')
'banana'
>>> remove_letter('i', 'Mississippi')
'Msssspp'
"""
without_letter = ""
for c in strng:
if c not in letter:
without_letter += c
return without_letter
def is_palindrome(s):
"""
>>> is_palindrome('abba')
True
>>> is_palindrome('abab')
False
>>> is_palindrome('tenet')
True
>>> is_palindrome('banana')
False
>>> is_palindrome('straw warts')
True
"""
half = len(s)/2
fronthalf = s[:half]
backhalf = s[-half:] #N.B no need to compare middle letter
return fronthalf == reverse(backhalf)
# We can make this even simpler by not bothering to split the word
# into halves. Simplest solution is the single line:
# return s == reverse(s)
# This will return True if word is the same forwards as backwards.
# Although might be slower for v. long words?
def count(sub, s):
"""
>>> count('is', 'Mississippi')
2
>>> count('an', 'banana')
2
>>> count('ana', 'banana')
2
>>> count('nana', 'banana')
1
>>> count('nanan', 'banana')
0
"""
count = 0
x = s.find(sub)
while x != -1:
count += 1
x = s.find(sub, x + 1)
return count
def remove(sub, s):
"""
>>> remove('an', 'banana')
'bana'
>>> remove('cyc', 'bicycle')
'bile'
>>> remove('iss', 'Mississippi')
'Missippi'
>>> remove('egg', 'bicycle')
'bicycle'
"""
x = s.find(sub)
if x != -1:
out1 = s[:x]
y = len(sub)
out2 = s[x + y:]
return out1 + out2
else:
return s
def remove_all(sub, s):
"""
>>> remove_all('an', 'banana')
'ba'
>>> remove_all('cyc', 'bicycle')
'bile'
>>> remove_all('iss', 'Mississippi')
'Mippi'
>>> remove_all('eggs', 'bicycle')
'bicycle'
"""
while s.find(sub) != -1:
s = remove(sub, s)
return s
if __name__ == '__main__':
import doctest
doctest.testmod()
>>> "%s %d %f" % (5, 5, 5)
'5 5 5.000000'
#note %f outputs 6 decimal places of 0s
>>> "%-.2f" % 3
'3.00'
#note .2 before f causes decimal output at 2 places (.00)
>>> "%-10.2f%-10.2f" % (7, 1.0/2)
'7.00 0.50 '
#note "The - after each % in the converstion specifications indicates left justification.
#The numerical values specify the minimum length,
#so %-13d is a left justified number at least 13 characters wide."
#Here if we count from index 0 @ 7 we will reach to index 10, before
#the next string formatting operator
>>> print " $%5.2fn $%5.2fn $%5.2f" % (3, 4.5, 11.2)
$ 3.00n $ 4.50n $11.20
>>> "%s %s %s %s" % ('this', 'that', 'something')
Traceback (most recent call last):
File "<pyshell#24>", line 1, in <module>
"%s %s %s %s" % ('this', 'that', 'something')
TypeError: not enough arguments for format string
>>> "%s %s %s" % ('this', 'that', 'something')
'this that something'
>>> "%s %s %s" % ('yes', 'no', 'up', 'down')
Traceback (most recent call last):
File "<pyshell#27>", line 1, in <module>
"%s %s %s" % ('yes', 'no', 'up', 'down')
TypeError: not all arguments converted during string formatting
>>> "%s %s %s %s" % ('yes', 'no', 'up', 'down')
'yes no up down'
>>> "%d %f %f" % (3, 3, "three")
Traceback (most recent call last):
File "<pyshell#29>", line 1, in <module>
"%d %f %f" % (3, 3, "three")
TypeError: float argument required, not str
>>> "%d %f %f" % (3, 3, 3)
'3 3.000000 3.000000'
尚未完全完成，但...
<syntaxhighlight lang="python">
fruit = "banana"
def count_letters(array, n):
count = 0
for i in range(len(array)):
m = array.find(n,i)
if( i == m ):
count += 1
print(count)
count_letters(fruit,"a")
x = ['spam!', 1, ['Brie', 'Roquefort', 'Pol le Veq'], [1, 2, 3]]
for i in x:
print len(i)
>>>
5
Traceback (most recent call last):
File "C:\Python26\ch9.py", line 5, in <module>
print len(i)
TypeError: object of type 'int' has no len()
>>>
x = ['spam!', 'one', ['Brie', 'Roquefort', 'Pol le Veq'], [1, 2, 3]]
for i in x:
print len(i)
>>>
5
3
3
3
>>>
"""
>>> a_list[3]
42
>>> a_list[6]
'Ni!'
>>> len(a_list)
8
"""
a_list = [1, 2, 3, 42, 5, 6, 'Ni!', 8]
if __name__ == '__main__':
import doctest
doctest.testmod()
"""
>>> b_list[1:]
['Stills', 'Nash']
>>> group = b_list + c_list
>>> group[-1]
'Young'
"""
b_list = ['Crosby', 'Stills', 'Nash']
c_list = ['Young']
if __name__ == '__main__':
import doctest
doctest.testmod()
"""
>>> 'war' in mystery_list
False
>>> 'peace' in mystery_list
True
>>> 'justice' in mystery_list
True
>>> 'oppression' in mystery_list
False
>>> 'equality' in mystery_list
True
"""
mystery_list = ['peace', 'justice', 'equality']
if __name__ == '__main__':
import doctest
doctest.testmod()
"""
>>> range(a, b, c)
[5, 9, 13, 17]
"""
a = 5
b = 18
c = 4
if __name__ == '__main__':
import doctest
doctest.testmod()
>>> range(10, 0, -2)
[10, 8, 6, 4, 2]
如果 start 小于 stop 且 step 小于 0 会发生什么？
结果将是一个空列表。
编写一个关于 start、stop 和 step 之间关系的规则。
>>> a = [1, 2, 3]
>>> b = a[:]
>>> id(a)
18484400
>>> id(b)
18594872
>>> b[0]
1
>>> b[0] = 5
>>> id(a)
18484400
>>> id(b)
18594872
>>> b
[5, 2, 3]
>>> a
[1, 2, 3]
>>> this = ['I', 'am', 'not', 'a', 'crook']
>>> that = ['I', 'am', 'not', 'a', 'crook']
>>> print "Test 1: %s" % (id(this) == id(that))
Test 1: False
>>> that = this
>>> print "Test 2: %s" % (id(this) == id(that))
Test 2: True
>>>
"""
>>> 13 in junk
True
>>> del junk[4]
>>> junk
[3, 7, 9, 10, 17, 21, 24, 27]
>>> del junk[a:b]
>>> junk
[3, 7, 27]
"""
junk = [3, 7, 9, 10, 13, 17, 21, 24, 27]
a = 2
b = (len(junk) - 2)
if __name__ == '__main__':
import doctest
doctest.testmod()
"""
>>> nlist[2][1]
0
>>> nlist[0][2]
17
>>> nlist[1][1]
5
"""
nlist = [[1, 2, 17], [4, 5, 6], [7, 0, 9]]
if __name__ == '__main__':
import doctest
doctest.testmod()
"""
>>> import string
>>> string.split(message, '??')
['this', 'and', 'that']
"""
message = "this??and??that"
if __name__ == '__main__':
import doctest
doctest.testmod()
def add_vectors(u, v):
"""
>>> add_vectors([1, 0], [1, 1])
[2, 1]
>>> add_vectors([1, 2], [1, 4])
[2, 6]
>>> add_vectors([1, 2, 1], [1, 4, 3])
[2, 6, 4]
>>> add_vectors([11, 0, -4, 5], [2, -4, 17, 0])
[13, -4, 13, 5]
"""
new_list = []
for index, value in enumerate(u):
for index2, value2 in enumerate(v):
if index == index2:
new_list += [value + value2]
return new_list
#However, a less complex solution follows:
new_list = []
for index, value in enumerate(u):
new_list += [u[index] + z[index]]
return new_list
if __name__ == '__main__':
import doctest
doctest.testmod()
def mult_lists(a, b):
"""
>>> mult_lists([1, 1], [1, 1])
2
>>> mult_lists([1, 2], [1, 4])
9
>>> mult_lists([1, 2, 1], [1, 4, 3])
12
"""
sm = 0
new_list = []
for x, elmt1 in enumerate(a):
for y, elmt2 in enumerate(b):
if x == y:
new_list += [elmt1 * elmt2]
q = len(new_list) - 1
while q != -1:
sm += new_list[q]
q += -1
return sm
if __name__ == '__main__':
import doctest
doctest.testmod()
#Simpler Code
#new_list = []
#for index, value in enumerate(b):
#new_list += [a*value]
#return new_list
def add_row(matrix):
"""
>>> m = [[0, 0], [0, 0]]
>>> add_row(m)
[[0, 0], [0, 0], [0, 0]]
>>> n = [[3, 2, 5], [1, 4, 7]]
>>> add_row(n)
[[3, 2, 5], [1, 4, 7], [0, 0, 0]]
>>> n
[[3, 2, 5], [1, 4, 7]]
"""
y = len(matrix[0])
matrix2 = matrix[:]
for z in range(1):
matrix2 += [[0] * y]
return matrix2
if __name__ == '__main__':
import doctest
doctest.testmod()
def add_column(matrix):
"""
>>> m = [[0, 0], [0, 0]]
>>> add_column(m)
[[0, 0, 0], [0, 0, 0]]
>>> n = [[3, 2], [5, 1], [4, 7]]
>>> add_column(n)
[[3, 2, 0], [5, 1, 0], [4, 7, 0]]
>>> n
[[3, 2], [5, 1], [4, 7]]
"""
x = len(matrix)
matrix2 = [d[:] for d in matrix]
for z in range(x):
matrix2[z] += [0]
return matrix2
if __name__ == '__main__':
import doctest
doctest.testmod()
def add_matrices(m1, m2):
"""
>>> a = [[1, 2], [3, 4]]
>>> b = [[2, 2], [2, 2]]
>>> add_matrices(a, b)
[[3, 4], [5, 6]]
>>> c = [[8, 2], [3, 4], [5, 7]]
>>> d = [[3, 2], [9, 2], [10, 12]]
>>> add_matrices(c, d)
[[11, 4], [12, 6], [15, 19]]
>>> c
[[8, 2], [3, 4], [5, 7]]
>>> d
[[3, 2], [9, 2], [10, 12]]
"""
new_matrix = []
for i, row in enumerate(m1):
new_row = []
for j, m1_value in enumerate(row):
m2_value = m2[i][j]
new_row += [m1_value + m2[i][j]]
new_matrix += [new_row]
return new_matrix
if __name__ == '__main__':
import doctest
doctest.testmod()
def scalar_mult(n, m):
"""
>>> a = [[1, 2], [3, 4]]
>>> scalar_mult(3, a)
[[3, 6], [9, 12]]
>>> b = [[3, 5, 7], [1, 1, 1], [0, 2, 0], [2, 2, 3]]
>>> scalar_mult(10, b)
[[30, 50, 70], [10, 10, 10], [0, 20, 0], [20, 20, 30]]
>>> b
[[3, 5, 7], [1, 1, 1], [0, 2, 0], [2, 2, 3]]
"""
new_matrix = []
for row in m:
new_row = []
for value in row:
new_row += [value*n]
new_matrix += [new_row]
return new_matrix
if __name__ == '__main__':
import doctest
doctest.testmod()
# Once we have obtained lists for the relevant rows and columns
# in row_times_column function, we will re-use the mult_lists
# function from question 8:
def mult_lists(a, b):
sum = 0
for i, a_value in enumerate(a):
sum += a_value * b[i]
return sum
def row_times_column(m1, row, m2, column):
"""
>>> row_times_column([[1, 2], [3, 4]], 0, [[5, 6], [7, 8]], 0)
19
>>> row_times_column([[1, 2], [3, 4]], 0, [[5, 6], [7, 8]], 1)
22
>>> row_times_column([[1, 2], [3, 4]], 1, [[5, 6], [7, 8]], 0)
43
>>> row_times_column([[1, 2], [3, 4]], 1, [[5, 6], [7, 8]], 1)
50
"""
m1_row = m1[row]
m2_col = []
for m2_row in m2:
m2_col += [m2_row[column]]
return mult_lists(m1_row, m2_col)
#This code may also be used to bypass the mult_lists code
def row_times_column(m1, row, m2, column):
x = 0
y = 0
for a in m1[row]:
t = a * m2[x][column]
y += t
x += 1
return y
def matrix_mult(m1, m2):
"""
>>> matrix_mult([[1, 2], [3, 4]], [[5, 6], [7, 8]])
[[19, 22], [43, 50]]
>>> matrix_mult([[1, 2, 3], [4, 5, 6]], [[7, 8], [9, 1], [2, 3]])
[[31, 19], [85, 55]]
>>> matrix_mult([[7, 8], [9, 1], [2, 3]], [[1, 2, 3], [4, 5, 6]])
[[39, 54, 69], [13, 23, 33], [14, 19, 24]]
"""
#To pass these tests, the function needs to multiply each each m1 row
#by each m2 column, to produce a new matrix with with the same number
#of rows as m1, and the same number of columns as m2. (This is the way
#matrices are commonly multiplied in mathematics). We can use
#row_times_column for each row/column combination
m1_num_rows = len(m1)
m2_num_cols = len(m2[0])
product_matrix = []
for row in range(m1_num_rows):
new_row = []
for column in range(m2_num_cols):
new_row += [row_times_column(m1, row, m2, column)]
product_matrix += [new_row]
return product_matrix
if __name__ == '__main__':
import doctest
doctest.testmod()
import string
def replace(s, old, new):
"""
>>> replace('Mississippi', 'i', 'I')
'MIssIssIppI'
>>> s = 'I love spom! Spom is my favorite food. Spom, spom, spom, yum!'
>>> replace(s, 'om', 'am')
'I love spam! Spam is my favorite food. Spam, spam, spam, yum!'
>>> replace(s, 'o', 'a')
'I lave spam! Spam is my favarite faad. Spam, spam, spam, yum!'
"""
s_without_old = string.split(s, old)
s_with_new = string.join(s_without_old, new)
return s_with_new
if __name__ == '__main__':
import doctest
doctest.testmod()
你也可以做
def myreplace(s, old, new):
"""
>>> myreplace('Mississippi', 'i', 'I')
'MIssIssIppI'
>>> s = 'I love spom! Spom is my favorite food. Spom, spom, spom, yum!'
>>> myreplace(s, 'om', 'am')
'I love spam! Spam is my favorite food. Spam, spam, spam, yum!'
>>> myreplace(s, 'o', 'a')
'I lave spam! Spam is my favarite faad. Spam, spam, spam, yum!'
"""
new_string = ""
counter = 0
while counter<len(s):
# check if old equals a slice of len(old)
if old == s[counter:counter+len(old)]:
new_string += new #s[counter+len(old):]
counter+=len(old)
else:
new_string += s[counter]
counter += 1
return new_string
if __name__ == '__main__':
import doctest
doctest.testmod(verbose=True)
>>> import calendar
>>> year = calendar.calendar(2008)
>>> print year
2008
January February March
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 1 2 3 1 2
7 8 9 10 11 12 13 4 5 6 7 8 9 10 3 4 5 6 7 8 9
14 15 16 17 18 19 20 11 12 13 14 15 16 17 10 11 12 13 14 15 16
21 22 23 24 25 26 27 18 19 20 21 22 23 24 17 18 19 20 21 22 23
28 29 30 31 25 26 27 28 29 24 25 26 27 28 29 30
31
April May June
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 1 2 3 4 1
7 8 9 10 11 12 13 5 6 7 8 9 10 11 2 3 4 5 6 7 8
14 15 16 17 18 19 20 12 13 14 15 16 17 18 9 10 11 12 13 14 15
21 22 23 24 25 26 27 19 20 21 22 23 24 25 16 17 18 19 20 21 22
28 29 30 26 27 28 29 30 31 23 24 25 26 27 28 29
30
July August September
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 1 2 3 1 2 3 4 5 6 7
7 8 9 10 11 12 13 4 5 6 7 8 9 10 8 9 10 11 12 13 14
14 15 16 17 18 19 20 11 12 13 14 15 16 17 15 16 17 18 19 20 21
21 22 23 24 25 26 27 18 19 20 21 22 23 24 22 23 24 25 26 27 28
28 29 30 31 25 26 27 28 29 30 31 29 30
October November December
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 1 2 1 2 3 4 5 6 7
6 7 8 9 10 11 12 3 4 5 6 7 8 9 8 9 10 11 12 13 14
13 14 15 16 17 18 19 10 11 12 13 14 15 16 15 16 17 18 19 20 21
20 21 22 23 24 25 26 17 18 19 20 21 22 23 22 23 24 25 26 27 28
27 28 29 30 31 24 25 26 27 28 29 30 29 30 31
>>>
isleap(year) - 返回闰年为 1，非闰年为 0。
>>> from calendar import *
>>> isleap(2008)
True
>>> isleap(2009)
False
>>>
python C:\Python26\Lib\pydoc.py -p 7464
math 模块中有 35 个函数。
floor 函数找到小于或等于 x 的最大整数。ceil 函数找到大于或等于 x 的最小整数。
math 模块中的两个数据常量是：'e' 和 'pi'。
"""
Interface summary:
import copy
x = copy.copy(y) # make a shallow copy of y
x = copy.deepcopy(y) # make a deep copy of y
For module specific errors, copy.Error is raised.
The difference between shallow and deep copying is only relevant for
compound objects (objects that contain other objects, like lists or
class instances).
- A shallow copy constructs a new compound object and then (to the
extent possible) inserts *the same objects* into it that the
original contains.
- A deep copy constructs a new compound object and then, recursively,
inserts *copies* into it of the objects found in the original."""
deepcopy 在你不需要解决的关于对象引用的练习中会派上用场，因此这里不需要答案。
命名空间是一个很棒的想法——我们应该多做一些！
def matrix_mult(m1, m2)
"""
>>> matrix_mult([[1, 2], [3, 4]], [[5, 6], [7, 8]])
[[19, 22], [43, 50]]
>>> matrix_mult([[1, 2, 3], [4, 5, 6]], [[7, 8], [9, 1], [2, 3]])
[[31, 19], [85, 55]]
>>> matrix_mult([[7, 8], [9, 1], [2, 3]], [[1, 2, 3], [4, 5, 6]])
[[39, 54, 69], [13, 23, 33], [14, 19, 24]]
"""
qr = len(m1)
qc = len(m2[0])
NewMtx = []
for row in range(qr):
newRow = []
for column in range(qc):
newRow.append(row_times_column(m1, row, m2, column))
NewMtx.append(newRow)
return NewMtx
return NewMtx
qr = len(m1)
qc = len(m2[0])
NewMtx = []
for row in range(qr):
newRow = []
for column in range(qc):
newRow.append(row_times_column(m1, row, m2, column))
NewMtx.append(newRow)
def myreplace(old, new, s):
"""
Replace all occurences of old with new in the string s.
>>> myreplace(',', ';', 'this, that, and, some, other, thing')
'this; that; and; some; other; thing'
>>> myreplace(' ', '**', 'Words will now be separated by stars.')
'Words**will**now**be**separated**by**stars.'
"""
old_removed = s.split(old)
new_added = new.join(old_removed)
return new_added
# Shorter version
# new_added = new.join(s.split(old))
def cleanword(word):
"""
>>> cleanword('what?')
'what'
>>> cleanword('"now!"')
'now'
>>> cleanword('?+="word!,@$()"')
'word'
"""
cleaned_word = ''
for i in range(len(word)):
char = word[i]
if char.isalpha():
cleaned_word += char
return cleaned_word
def has_dashdash(s):
"""
>>> has_dashdash('distance--but')
True
>>> has_dashdash('several')
False
>>> has_dashdash('critters')
False
>>> has_dashdash('spoke--fancy')
True
>>> has_dashdash('yo-yo')
False
"""
return s.find('--') != -1
def extract_words(s):
"""
>>> extract_words('Now is the time! "Now", is the time? Yes, now.')
['now', 'is', 'the', 'time', 'now', 'is', 'the', 'time', 'yes', 'now']
>>> extract_words('she tried to curtsey as she spoke--fancy')
['she', 'tried', 'to', 'curtsey', 'as', 'she', 'spoke', 'fancy']
"""
if has_dashdash(s):
s = myreplace('--', ' ', s) #using myreplace function from Q. 10
words_punc = s.split()
cleanlist = []
for word in words_punc:
cleanedword = cleanword(word).lower()
cleanlist.append(cleanedword)
return cleanlist
def wordcount(word, wordlist):
"""
>>> wordcount('now', ['now', 'is', 'time', 'is', 'now', 'is', 'is'])
['now', 2]
>>> wordcount('is', ['now', 'is', 'time', 'is', 'now', 'is', 'the', 'is'])
['is', 4]
>>> wordcount('time', ['now', 'is', 'time', 'is', 'now', 'is', 'is'])
['time', 1]
>>> wordcount('frog', ['now', 'is', 'time', 'is', 'now', 'is', 'is'])
['frog', 0]
"""
return [word, wordlist.count(word)]
def wordset(wordlist):
"""
>>> wordset(['now', 'is', 'time', 'is', 'now', 'is', 'is'])
['is', 'now', 'time']
>>> wordset(['I', 'a', 'a', 'is', 'a', 'is', 'I', 'am'])
['I', 'a', 'am', 'is']
>>> wordset(['or', 'a', 'am', 'is', 'are', 'be', 'but', 'am'])
['a', 'am', 'are', 'be', 'but', 'is', 'or']
"""
for word in wordlist:
count = wordcount(word, wordlist)[1]
if count > 1:
for a in range(count - 1):
wordlist.remove(word)
wordlist.sort()
return wordlist
def longestword(wordset):
"""
>>> longestword(['a', 'apple', 'pear', 'grape'])
5
>>> longestword(['a', 'am', 'I', 'be'])
2
>>> longestword(['this', 'that', 'supercalifragilisticexpialidocious'])
34
"""
longest = 0
for word in wordset:
length = len(word)
if length > longest:
longest = length
return longest
if __name__ == '__main__':
import doctest
doctest.testmod()
#sort_fruits.py
source = open('unsorted_fruits.txt', 'r')
fruits = source.readlines()
source.close()
fruits.sort()
newfile = open('sorted_fruits.txt', 'w')
newfile.writelines(fruits)
newfile.close()
#mean.py
from sys import argv
nums = argv[1:]
for i, value in enumerate(nums):
nums[i] = float(value)
mean = sum(nums) / len(nums)
print mean
#median.py
from sys import argv
nums = argv[1:]
for i, value in enumerate(nums):
nums[i] = float(value)
nums.sort()
size = len(nums)
middle = size / 2
if size % 2 == 0:
median = (nums[middle - 1] + nums[middle]) / 2
else:
median = nums[middle]
if median == float(int(median)):
median = int(median)
print median
#
# countletters.py
#
def display(i):
if i == 10: return 'LF'
if i == 13: return 'CR'
if i == 32: return 'SPACE'
return chr(i)
from sys import argv
filename = argv[1]
infile = open(filename, 'r')
text = infile.read()
infile.close()
counts = 128 * [0]
for letter in text:
counts[ord(letter)] += 1
filenamesplit = filename.split('.') # splits 'name.txt' -> ['name', 'txt']
count_file = filenamesplit[0] + '_counts.dat' # 'name' -> 'name_counts.dat'
outfile = open(count_file, 'w')
outfile.write("%-12s%s\n" % ("Character", "Count"))
outfile.write("=================\n")
for i in range(len(counts)):
if counts[i]:
outfile.write("%-12s%d\n" % (display(i), counts[i]))
outfile.close()
#
#seqtools.py
#
def remove_at(pos, seq):
return seq[:pos] + seq[pos+1:]
def encapsulate(val, seq):
"""
>>> encapsulate((1, 'a'), [0 , 'b'])
[(1, 'a')]
>>> encapsulate(42, 'string')
'42'
>>> tup = 1, 2, 3 # NB. Testmod seems to report this
>>> encapsulate(5, tup) # as a fail, despite returning the
(5,) # correct result?
"""
if type(seq) == type(""):
return str(val)
if type(seq) == type([]):
return [val]
return (val,)
def insert_in_middle(val, seq):
"""
>>> insert_in_middle('two', (1,3))
(1, 'two', 3)
>>> insert_in_middle(4, 'two six')
'two 4 six'
>>> insert_in_middle((2, 4), [(1, 2), (3, 6)])
[(1, 2), (2, 4), (3, 6)]
"""
middle = len(seq)/2
return seq[:middle] + encapsulate(val, seq) + seq[middle:]
def make_empty(seq):
"""
>>> make_empty([1, 2, 3, 4])
[]
>>> make_empty(('a', 'b', 'c'))
()
>>> make_empty("No, not me!")
''
"""
if type(seq) == type(""):
return ''
if type(seq) == type([]):
return []
return ()
def insert_at_end(val, seq):
"""
>>> insert_at_end(5, [1, 3, 4, 6])
[1, 3, 4, 6, 5]
>>> insert_at_end('x', 'abc')
'abcx'
>>> insert_at_end(5, (1, 3, 4, 6)) # NB. Testmod seems to report this as a fail
(1, 3, 4, 6, 5) # despite returning the correct result
"""
return seq + encapsulate(val, seq)
def insert_in_front(val, seq):
"""
>>> insert_in_front(5, [1, 3, 4, 6])
[5, 1, 3, 4, 6]
>>> insert_in_front(5, (1, 3, 4, 6))
(5, 1, 3, 4, 6)
>>> insert_in_front('x', 'abc')
'xabc'
"""
return encapsulate(val, seq) + seq
def index_of(val, seq, start=0):
"""
>>> index_of(9, [1, 7, 11, 9, 10])
3
>>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5))
3
>>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
6
>>> index_of('y', 'happy birthday')
4
>>> index_of('banana', ['apple', 'banana', 'cherry', 'date'])
1
>>> index_of(5, [2, 3, 4])
-1
>>> index_of('b', ['apple', 'banana', 'cherry', 'date'])
-1
"""
for i in range(start, len(seq)):
if seq[i] == val:
return i
return -1
def remove_at(index, seq):
"""
>>> remove_at(3, [1, 7, 11, 9, 10])
[1, 7, 11, 10]
>>> remove_at(5, (1, 4, 6, 7, 0, 9, 3, 5))
(1, 4, 6, 7, 0, 3, 5)
>>> remove_at(2, "Yomrktown")
'Yorktown'
"""
return seq[:index] + seq[index + 1:]
def remove_val(val, seq):
"""
>>> remove_val(11, [1, 7, 11, 9, 10])
[1, 7, 9, 10]
>>> remove_val(15, (1, 15, 11, 4, 9))
(1, 11, 4, 9)
>>> remove_val('what', ('who', 'what', 'when', 'where', 'why', 'how'))
('who', 'when', 'where', 'why', 'how')
"""
return remove_at(index_of(val, seq), seq)
def remove_all(val, seq):
"""
>>> remove_all(11, [1, 7, 11, 9, 11, 10, 2, 11])
[1, 7, 9, 10, 2]
>>> remove_all('i', 'Mississippi')
'Msssspp'
"""
while index_of(val, seq) != -1:
seq = remove_val(val, seq)
return seq
def count(val, seq):
"""
>>> count(5, (1, 5, 3, 7, 5, 8, 5))
3
>>> count('s', 'Mississippi')
4
>>> count((1, 2), [1, 5, (1, 2), 7, (1, 2), 8, 5])
2
"""
count = 0
for item in seq:
if item == val:
count += 1
return count
def reverse(seq):
"""
>>> reverse([1, 2, 3, 4, 5])
[5, 4, 3, 2, 1]
>>> reverse(('shoe', 'my', 'buckle', 2, 1))
(1, 2, 'buckle', 'my', 'shoe')
>>> reverse('Python')
'nohtyP'
"""
output = make_empty(seq)
for item in seq:
output = insert_in_front(item, output)
return output
def sort_sequence(seq):
"""
>>> sort_sequence([3, 4, 6, 7, 8, 2])
[2, 3, 4, 6, 7, 8]
>>> sort_sequence((3, 4, 6, 7, 8, 2))
(2, 3, 4, 6, 7, 8)
>>> sort_sequence("nothappy")
'ahnoppty'
"""
listseq = list(seq)
listseq.sort()
output = make_empty(seq)
for item in listseq:
output = insert_at_end(item, output)
return output
def recursive_min(nested_num_list):
"""
>>> recursive_min([2, 9, [1, 13], 8, 6])
1
>>> recursive_min([2, [[100, 1], 90], [10, 13], 8, 6])
1
>>> recursive_min([2, [[13, -7], 90], [1, 100], 8, 6])
-7
>>> recursive_min([[[-13, 7], 90], 2, [1, 100], 8, 6])
-13
"""
smallest = nested_num_list[0]
while type(smallest) == type([]):
smallest = smallest[0]
for element in nested_num_list:
if type(element) == type([]):
min_of_elem = recursive_min(element)
if smallest > min_of_elem:
smallest = min_of_elem
else:
if smallest > element:
smallest = element
return smallest
def recursive_count(target, nested_num_list):
"""
>>> recursive_count(2, [2, 9, [2, 1, 13, 2], 8, [2, 6]])
4
>>> recursive_count(7, [[9, [7, 1, 13, 2], 8], [7, 6]])
2
>>> recursive_count(15, [[9, [7, 1, 13, 2], 8], [2, 6]])
0
>>> recursive_count(5, [[5, [5, [1, 5], 5], 5], [5, 6]])
6
"""
count = 0
for element in nested_num_list:
if type(element) == type([]):
count += recursive_count(target, element)
else:
if element == target:
count += 1
return count
def flatten(nested_num_list):
"""
>>> flatten([2, 9, [2, 1, 13, 2], 8, [2, 6]])
[2, 9, 2, 1, 13, 2, 8, 2, 6]
>>> flatten([[9, [7, 1, 13, 2], 8], [7, 6]])
[9, 7, 1, 13, 2, 8, 7, 6]
>>> flatten([[9, [7, 1, 13, 2], 8], [2, 6]])
[9, 7, 1, 13, 2, 8, 2, 6]
>>> flatten([[5, [5, [1, 5], 5], 5], [5, 6]])
[5, 5, 1, 5, 5, 5, 5, 6]
"""
flat_num_list = []
for element in nested_num_list:
if type(element) == type([]):
flat_num_list += flatten(element)
else:
flat_num_list += [element]
return flat_num_list
def readposint(prompt = 'Please enter a positive integer: '):
while True:
posint = raw_input(prompt)
try:
posint = float(posint)
if posint != int(posint):
raise ValueError, '%s is not an integer' % posint
elif posint < 1:
raise ValueError, '%s is not positive' % posint
break
except:
print '%s is not a positive integer. Try again.' % posint
return int(posint)
def factorial(n):
nshriek = 1 # n factorial is sometimes called
while n > 1: # 'n shriek' because of the 'n!' notation
nshriek *= n
n -= 1
return nshriek
#
# litter.py
#
import os
import sys
def getroot():
if len(sys.argv) == 1:
path = ''
else:
path = sys.argv[1]
if os.path.isabs(path):
tree_root = path
else:
tree_root = os.path.join(os.getcwd(), path)
return tree_root
def getdirlist(path):
dirlist = os.listdir(path)
dirlist = [name for name in dirlist if name[0] != '.']
dirlist.sort()
return dirlist
def traverse(path, t=0):
dirlist = getdirlist(path)
for num, file in enumerate(dirlist):
dirsize = len(dirlist)
path2file = os.path.join(path, file)
if os.path.isdir(path2file):
t += 1
newtrash = open(path2file + '\\trash.txt', 'w')
newtrash.close()
if getdirlist(path2file):
t = traverse(path2file, t)
return t
if __name__ == '__main__':
root = getroot()
trashes = traverse(root)
if trashes == 1:
filestring = 'file'
else:
filestring = 'files'
print '%d trash.txt %s created' % (trashes, filestring)
#
# cleanup.py
#
import os
import sys
def getroot():
if len(sys.argv) == 1:
path = ''
else:
path = sys.argv[1]
if os.path.isabs(path):
tree_root = path
else:
tree_root = os.path.join(os.getcwd(), path)
return tree_root
def getdirlist(path):
dirlist = os.listdir(path)
dirlist = [name for name in dirlist if name[0] != '.']
dirlist.sort()
return dirlist
def traverse(path, t = 0):
dirlist = getdirlist(path)
for num, file in enumerate(dirlist):
dirsize = len(dirlist)
path2file = os.path.join(path, file)
if file == 'trash.txt':
t += 1
os.remove(path2file)
elif os.path.isdir(path2file):
t += traverse(path2file)
return t
if __name__ == '__main__':
root = getroot()
trashed = traverse(root)
if trashed == 1:
filestring = 'file'
else:
filestring = 'files'
print '%d trash.txt %s deleted' % (trashed, filestring)
#
# letter_counts.py
#
import sys
def count_letters(s):
letter_counts = {}
for letter in s:
if letter.isalpha():
letter_counts[letter.lower()] = letter_counts.get(letter.lower(), 0) + 1
return letter_counts
def print_counts(letter_counts):
letter_items = letter_counts.items()
letter_items.sort()
for item in letter_items:
print item[0], item[1]
if len(sys.argv) > 1:
letter_counts = count_letters(sys.argv[1])
print_counts(letter_counts)
else:
print 'No argument supplied'
def add_fruit(inventory, fruit, quantity=0):
"""
Adds quantity of fruit to inventory.
>>> new_inventory = {}
>>> add_fruit(new_inventory, 'strawberries', 10)
>>> new_inventory.has_key('strawberries')
True
>>> new_inventory['strawberries']
10
>>> add_fruit(new_inventory, 'strawberries', 25)
>>> new_inventory['strawberries']
35
"""
if inventory.has_key(fruit):
inventory[fruit] += quantity
else:
inventory[fruit] = quantity
#
# alice_words.py
#
import string
filename = 'alice_in_wonderland.txt'
countfile = 'alice_counts.txt'
def add_word(counts, word):
if counts.has_key(word):
counts[word] += 1
else:
counts[word] = 1
def get_word(item):
word = ''
item = item.strip(string.digits)
item = item.lstrip(string.punctuation)
item = item.rstrip(string.punctuation)
word = item.lower()
return word
def count_words(text):
text = ' '.join(text.split('--')) #replace '--' with a space
items = text.split() #leaves in leading and trailing punctuation,
#'--' not recognised by split() as a word separator
counts = {}
for item in items:
word = get_word(item)
if not word == '':
add_word(counts, word)
return counts
infile = open(filename, 'r')
text = infile.read()
infile.close()
counts = count_words(text)
outfile = open(countfile, 'w')
outfile.write("%-18s%s\n" %("Word", "Count"))
outfile.write("=======================\n")
counts_list = counts.items()
counts_list.sort()
for word in counts_list:
outfile.write("%-18s%d\n" %(word[0], word[1]))
outfile.close
单词 "alice" 出现了 386 次（不包括 12 次 "alice's"）
列表中最长的 "单词" 是 "bread-and-butter"，有 16 个字符。可以通过将以下代码添加到 alice_words.py 程序中来找到它
longest = ('', 0)
for word in counts:
if len(word) > longest[1]:
longest = (word, len(word))
print longest
稍微修改一下，我们可以找到最长的无连字符的单词 "disappointment"，它有 14 个字符。
longest = ('', 0)
for word in counts:
if len(word) > longest[1] and word.find('-') == -1
longest = (word, len(word))
print longest
- 日期: 2015-5-3
- 作者: [email protected]
- 此程序将反转任何给定文件的行
for line in reversed(open('test.txt').readlines()):
print(line.rstrip())
def distance(p1, p2):
dx = p2.x - p1.x
dy = p2.y - p1.y
dsquared = dx**2 + dy**2
result = dsquared**0.5
return result
def move_rect(rect, dx, dy):
rect.corner.x += dx
rect.corner.y += dy
def move_rect(rect, dx, dy):
import copy
new_rect = copy.deepcopy(rect)
new_rect.corner.x += dx
new_rect.corner.y += dy
return new_rect
def print_time(t):
print "%i:%i:%i" % (t.hours, t.minutes, t.seconds)
def after(t1, t2):
return convert_to_seconds(t1) > convert_to_seconds(t2)
def increment(time, seconds):
sum = convert_to_seconds(time) + seconds
newtime = make_time(sum)
time.hours = newtime.hours
time.minutes = newtime.minutes
time.seconds = newtime.seconds
>>> increment(t1, 180)
def increment(time, seconds):
sum = convert_to_seconds(time) + seconds
newtime = make_time(sum)
return newtime
>>> increment(t1, 180)
<__main__.Time instance at 0x91ceeac>
>>> t1 = increment(t1, 180)
class Time():
# other method definitions here
def convertToSeconds(self):
minutes = self.hours * 60 + self.minutes
seconds = minutes * 60 + self.seconds
return seconds
def find(str, ch, start=0, end = "None"):
index = start
if end == "None":
end = len(str)
while index < end:
if str[index] == ch:
return index
index = index + 1
return -1
class Card:
...
def __cmp__(self, other):
# check the suits
if self.suit > other.suit: return 1
if self.suit < other.suit: return -1
# suits are the same... check ranks
if self.rank > other.rank:
if other.rank == 1: return -1 #other is Ace (and self is not)
return 1
if self.rank < other.rank:
if self.rank == 1: return 1 #self is Ace (and other is not)
return -1
# ranks are the same... it's a tie
return 0
class OldMaidGame(CardGame):
...
def printHands(self):
for hand in self.hands:
print hand
def print_list(node):
s = '['
while node:
s += str(node.cargo)
node = node.next
if node:
s += ', '
s += ']'
print s
>>> print eval_postfix("1 2 + 3 *")
9
>>> print eval_postfix("1 2 3 * +")
7
class listQueue:
def __init__(self):
self.items = []
def is_empty(self):
return self.items == []
def insert(self, item):
self.items.append(item)
def remove(self):
if self.is_empty():
return None
return self.items.pop()
class llPriorityQueue:
def __init__(self): # NB, self.last is no longer needed because
self.length = 0 # the linked list will be ordered with
self.head = None # the next item to be removed at the head
def is_empty(self):
return (self.length == 0)
def insert(self, cargo): # insert() needs to keep the list ordered to
node = Node(cargo) # make remove() constant time. So insert()
if self.head == None: # must traverse the list. Now insert() is
self.head = node # linear time instead of remove()!
else:
if cargo > self.head.cargo:
node.next = self.head
self.head = node
else:
smaller = self.head
while smaller.cargo >= cargo:# traverse queue until we
previous = smaller # find first node with cargo
smaller = smaller.next # smaller than the new node
if smaller == None: #<--(or we get to the end
break # of the list)
previous.next = node # insert node ahead of first
node.next = smaller # smaller item
self.length += 1
def remove(self):
if self.is_empty():
return None
cargo = self.head.cargo
self.head = self.head.next
self.length = self.length - 1
return cargo
def print_tree_inorder(tree):
if tree == None: return
if tree.left:
print '(',
print_tree_inorder(tree.left),
print tree.cargo,
print_tree_inorder(tree.right),
if tree.right:
print ')',
# The output from this function is correct and unambiguous, but many
# brackets are not really necessary and look messy. For example:
>>> token_list =['(',3, '+', 7, ')', '*', '(', 5, '+', 3, ')', '+', 4, '*', 5, 'end']
>>> tree = get_sum(token_list)
>>> print_tree_inorder(tree)
( ( ( 3 + 7 ) * ( 5 + 3 ) ) + ( 4 * 5 ) )
# The ideal output would be something like: (3 + 7) * (5 + 3) + 4 * 5
def make_token_list(s):
token_list = []
for char in s:
if char == ' ':
continue
elif char.isdigit():
token_list.append(int(char))
else:
token_list.append(char)
token_list.append('end')
return token_list
# ... (only modified functions shown)
def dump(tree):
# returns string representation of tree in postfix-style
# order with commas separating nodes. Leaves are
# represented with two preceding commas, corresponding to
# the empty tree.left & tree.right attributes.
if tree == None: return ','
s = ''
s += dump(tree.left)
s += dump(tree.right)
s += str(tree) + ','
return s
def restore_tree(token_list):
# Recreate tree from token list generated from save file
cargo = token_list.pop()
if cargo == '': return
right = restore_tree(token_list)
left = restore_tree(token_list)
tree = Tree(cargo, left, right)
return tree
def animal():
#start with a singleton
root = Tree("bird")
# or use save file if it exists
try:
infile = open(savefile, 'r')
s = infile.read()
infile.close()
token_list = s.split(',')
token_list.pop() #remove empty item at end
root = restore_tree(token_list)
except IOError:
pass
# loop until the user quits
while True:
print
if not yes("Are you thinking of an animal? "): break
# walk the tree
tree = root
while tree.left != None:
prompt = tree.cargo + "? "
if yes(prompt):
tree = tree.right
else:
tree = tree.left
# make a guess
guess = tree.cargo
prompt = "Is it a " + guess + "? "
if yes(prompt):
print "Yatta!"
continue
# get new information
prompt = "What is the animal's name? "
animal = raw_input(prompt)
prompt = "What question would distinguish a %s from a %s? "
question = raw_input(prompt % (animal, guess)).strip('?').capitalize()
# add new information to the tree
tree.cargo = question
prompt = "If the animal were %s the answer would be? "
if yes(prompt % animal):
tree.left = Tree(guess)
tree.right = Tree(animal)
else:
tree.left = Tree(animal)
tree.right = Tree(guess)
# save the tree
s = dump(root)
outfile = open(savefile, 'w')
outfile.write(s)
outfile.close()