面向非程序员的 Python 2.6 教程/列表
您已经看到了存储单个值的普通变量。但是，其他类型的变量可以保存多个值。最简单的类型称为列表。以下是一个使用列表的示例
which_one = input("What month (1-12)? ")
months = ['January', 'February', 'March', 'April', 'May', 'June', 'July',
'August', 'September', 'October', 'November', 'December']
if 1 <= which_one <= 12:
print "The month is", months[which_one - 1]
以及一个输出示例
What month (1-12)? 3 The month is March
在这个例子中，months 是一个列表。months 通过以下几行代码定义： months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 和 'August', 'September', 'October', 'November', 'December']（注意，也可以使用 \ 来分割长行，但在这种情况下没有必要，因为 Python 足够智能，可以识别方括号内的一切都属于一起）。[ 和 ] 用逗号 (,) 分隔列表项来开始和结束列表。该列表在 months[which_one - 1] 中使用。列表由从 0 开始编号的项组成。换句话说，如果您想要 January，则使用 months[0]。给列表一个数字，它将返回存储在该位置的值。
语句 if 1 <= which_one <= 12: 只有在 which_one 包含在 1 到 12 之间时才为真（换句话说，如果您在代数中见过它，就会像您预期的那样）。
可以将列表看作是一系列盒子。每个盒子都有不同的值。例如，由 demolist = ['life', 42, 'the universe', 6, 'and', 9] 创建的盒子将如下所示
| 盒子编号 | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| demolist | "life" | 42 | "the universe" | 6 | "and" | 9 |
每个盒子都通过其编号来引用，因此语句 demolist[0] 将获取 'life'，demolist[1] 将获取 42，依此类推，直到 demolist[5] 获取 9。
以下示例只是为了展示列表可以执行的其他许多操作（这次我不希望您键入它，但您可能需要玩玩列表，直到您对它们感到满意）。以下是示例
demolist = ["life", 42, "the universe", 6, "and", 9]
print "demolist = ",demolist
demolist.append("everything")
print "after 'everything' was appended demolist is now:"
print demolist
print "len(demolist) =", len(demolist)
print "demolist.index(42) =", demolist.index(42)
print "demolist[1] =", demolist[1]
# Next we will loop through the list
c = 0
while c < len(demolist):
print "demolist[", c, "] =", demolist[c]
c = c + 1
del demolist[2]
print "After 'the universe' was removed demolist is now:"
print demolist
if "life" in demolist:
print "'life' was found in demolist"
else:
print "'life' was not found in demolist"
if "amoeba" in demolist:
print "'amoeba' was found in demolist"
if "amoeba" not in demolist:
print "'amoeba' was not found in demolist"
demolist.sort()
print "The sorted demolist is", demolist
输出是
demolist = ['life', 42, 'the universe', 6, 'and', 9] after 'everything' was appended demolist is now: ['life', 42, 'the universe', 6, 'and', 9, 'everything'] len(demolist) = 7 demolist.index(42) = 1 demolist[1] = 42 demolist[ 0 ] = life demolist[ 1 ] = 42 demolist[ 2 ] = the universe demolist[ 3 ] = 6 demolist[ 4 ] = and demolist[ 5 ] = 9 demolist[ 6 ] = everything After 'the universe' was removed demolist is now: ['life', 42, 6, 'and', 9, 'everything'] 'life' was found in demolist 'amoeba' was not found in demolist The sorted demolist is [6, 9, 42, 'and', 'everything', 'life']
此示例使用了一堆新函数。请注意，您可以直接 print 整个列表。接下来，append 函数用于在列表末尾添加一个新项目。len 返回列表中包含的项目数。列表的有效索引（如在 [] 内使用的数字）范围为 0 到 len - 1。index 函数告诉项目在列表中的第一个位置在哪里。请注意 demolist.index(42) 返回 1，而 demolist[1] 运行时返回 42。行 # Next we will loop through the list 只是对程序员的提醒（也称为注释）。Python 将忽略以 # 开头的任何行。接下来，以下几行
c = 0
while c < len(demolist):
print 'demolist[', c, '] =', demolist[c]
c = c + 1
创建一个变量 c，它从 0 开始，并不断递增，直到达到列表的最后一个索引。同时，print 语句打印出列表中的每个元素。del 命令可用于删除列表中的给定元素。接下来的几行使用 in 运算符来测试元素是否在列表中或不在列表中。sort 函数对列表进行排序。如果您需要按从小到大或按字母顺序排序的列表，这将很有用。请注意，这会重新排列列表。总之，对于列表，会发生以下操作
| 示例 | 解释 |
|---|---|
demolist[2]
|
访问索引 2 处的元素 |
demolist[2] = 3
|
将索引 2 处的元素设置为 3 |
del demolist[2]
|
删除索引 2 处的元素 |
len(demolist)
|
返回 demolist 的长度 |
"value" in demolist
|
如果为 True，则"value"是 demolist 中的元素 |
"value" not in demolist
|
如果 "value" 不是 demolist 中的元素，则为 True |
demolist.sort()
|
对 demolist 进行排序 |
demolist.index("value")
|
返回 "value" 第一次出现的索引 |
demolist.append("value")
|
在列表末尾添加一个元素 "value" |
demolist.remove("value")
|
从 demolist 中删除 value 的第一次出现（与 del demolist[demolist.index("value")] 相同） |
以下示例以更有用的方式使用这些功能
menu_item = 0
namelist = []
while menu_item != 9:
print "--------------------"
print "1. Print the list"
print "2. Add a name to the list"
print "3. Remove a name from the list"
print "4. Change an item in the list"
print "9. Quit"
menu_item = input("Pick an item from the menu: ")
if menu_item == 1:
current = 0
if len(namelist) > 0:
while current < len(namelist):
print current, ".", namelist[current]
current = current + 1
else:
print "List is empty"
elif menu_item == 2:
name = raw_input("Type in a name to add: ")
namelist.append(name)
elif menu_item == 3:
del_name = raw_input("What name would you like to remove: ")
if del_name in namelist:
# namelist.remove(del_name) would work just as fine
item_number = namelist.index(del_name)
del namelist[item_number]
# The code above only removes the first occurrence of
# the name. The code below from Gerald removes all.
# while del_name in namelist:
# item_number = namelist.index(del_name)
# del namelist[item_number]
else:
print del_name, "was not found"
elif menu_item == 4:
old_name = raw_input("What name would you like to change: ")
if old_name in namelist:
item_number = namelist.index(old_name)
new_name = raw_input("What is the new name: ")
namelist[item_number] = new_name
else:
print old_name, "was not found"
print "Goodbye"
以下是部分输出
-------------------- 1. Print the list 2. Add a name to the list 3. Remove a name from the list 4. Change an item in the list 9. Quit Pick an item from the menu: 2 Type in a name to add: Jack Pick an item from the menu: 2 Type in a name to add: Jill Pick an item from the menu: 1 0 . Jack 1 . Jill Pick an item from the menu: 3 What name would you like to remove: Jack Pick an item from the menu: 4 What name would you like to change: Jill What is the new name: Jill Peters Pick an item from the menu: 1 0 . Jill Peters Pick an item from the menu: 9 Goodbye
这是一个很长的程序。让我们看一下源代码。行 namelist = [] 使变量 namelist 成为一个没有项目（或元素）的列表。下一行重要的代码是 while menu_item != 9:。此行启动一个循环，该循环允许此程序的菜单系统。接下来的几行显示一个菜单，并决定要运行程序的哪个部分。
部分代码
current = 0
if len(namelist) > 0:
while current < len(namelist):
print current, ".", namelist[current]
current = current + 1
else:
print "List is empty"
遍历列表并打印每个名称。len(namelist) 告诉列表中包含多少个项目。如果 len 返回 0，则列表为空。
然后，在几行之后，出现语句 namelist.append(name)。它使用 append 函数在列表末尾添加一个项目。向下跳两行，请注意这段代码
item_number = namelist.index(del_name)
del namelist[item_number]
在这里，index 函数用于查找稍后将用于删除项目的索引值。del namelist[item_number] 用于删除列表的元素。
下一部分
old_name = raw_input("What name would you like to change: ")
if old_name in namelist:
item_number = namelist.index(old_name)
new_name = raw_input("What is the new name: ")
namelist[item_number] = new_name
else:
print old_name, "was not found"
使用 index 查找 item_number，然后将 new_name 放在 old_name 所在的位置。
恭喜您，现在您已经掌握了列表，您已经足够了解该语言，可以执行计算机可以执行的任何计算（这在技术上被称为图灵完备性）。当然，还有许多功能可以使您的生活更轻松。
test.py
## This program runs a test of knowledge
# First get the test questions
# Later this will be modified to use file io.
def get_questions():
# notice how the data is stored as a list of lists
return [["What color is the daytime sky on a clear day? ", "blue"],
["What is the answer to life, the universe and everything? ", "42"],
["What is a three letter word for mouse trap? ", "cat"]]
# This will test a single question
# it takes a single question in
# it returns True if the user typed the correct answer, otherwise False
def check_question(question_and_answer):
# extract the question and the answer from the list
question = question_and_answer[0]
answer = question_and_answer[1]
# give the question to the user
given_answer = raw_input(question)
# compare the user's answer to the testers answer
if answer == given_answer:
print "Correct"
return True
else:
print "Incorrect, correct was:", answer
return False
# This will run through all the questions
def run_test(questions):
if len(questions) == 0:
print "No questions were given."
# the return exits the function
return
index = 0
right = 0
while index < len(questions):
# Check the question
if check_question(questions[index]):
right = right + 1
index = index + 1
# go to the next question
else:
index = index + 1
# notice the order of the computation, first multiply, then divide
print "You got", right * 100 / len(questions),\
"% right out of", len(questions)
# now let's run the questions
run_test(get_questions())
值 True 和 False 分别指向 1 和 0。它们通常用于健全性检查、循环条件等。您将在稍后（章节 布尔表达式）了解有关此内容的更多信息。
示例输出
What color is the daytime sky on a clear day?green Incorrect, correct was: blue What is the answer to life, the universe and everything?42 Correct What is a three letter word for mouse trap?cat Correct You got 66 % right out of 3
扩展 test.py 程序，使其有一个菜单，提供进行测试、查看问题和答案列表以及退出选项。此外，添加一个新的问题，询问“真正的先进机器发出什么声音？”，答案是“ping”。
解决方案
扩展 test.py 程序，使其有一个菜单，提供进行测试、查看问题和答案列表以及退出选项。此外，添加一个新的问题，询问“真正的先进机器发出什么声音？”，答案是“ping”。
## This program runs a test of knowledge
questions = [["What color is the daytime sky on a clear day? ", "blue"],
["What is the answer to life, the universe and everything? ", "42"],
["What is a three letter word for mouse trap? ", "cat"],
["What noise does a truly advanced machine make?", "ping"]]
# This will test a single question
# it takes a single question in
# it returns True if the user typed the correct answer, otherwise False
def check_question(question_and_answer):
# extract the question and the answer from the list
question = question_and_answer[0]
answer = question_and_answer[1]
# give the question to the user
given_answer = raw_input(question)
# compare the user's answer to the testers answer
if answer == given_answer:
print "Correct"
return True
else:
print "Incorrect, correct was:", answer
return False
# This will run through all the questions
def run_test(questions):
if len(questions) == 0:
print "No questions were given."
# the return exits the function
return
index = 0
right = 0
while index < len(questions):
# Check the question
if check_question(questions[index]):
right = right + 1
# go to the next question
index = index + 1
# notice the order of the computation, first multiply, then divide
print "You got", right * 100 / len(questions),\
"% right out of", len(questions)
#showing a list of questions and answers
def showquestions(questions):
q = 0
while q < len(questions):
a = 0
print "Q:" , questions[q][a]
a = 1
print "A:" , questions[q][a]
q = q + 1
# now let's define the menu function
def menu():
print "-----------------"
print "Menu:"
print "1 - Take the test"
print "2 - View a list of questions and answers"
print "3 - View the menu"
print "5 - Quit"
print "-----------------"
choice = "3"
while choice != "5":
if choice == "1":
run_test(questions)
elif choice == "2":
showquestions(questions)
elif choice == "3":
menu()
print
choice = raw_input("Choose your option from the menu above: ")