面向非程式設計師的 Python 2.6 教程/列表
您已經看到了儲存單個值的普通變數。但是，其他型別的變數可以儲存多個值。最簡單的型別稱為列表。以下是一個使用列表的示例
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]
以及一個輸出示例
What month (1-12)? 3 The month is March
在這個例子中，months 是一個列表。months 透過以下幾行程式碼定義： months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 和 'August', 'September', 'October', 'November', 'December']（注意，也可以使用 \ 來分割長行，但在這種情況下沒有必要，因為 Python 足夠智慧，可以識別方括號內的一切都屬於一起）。[ 和 ] 用逗號 (,) 分隔列表項來開始和結束列表。該列表在 months[which_one - 1] 中使用。列表由從 0 開始編號的項組成。換句話說，如果您想要 January，則使用 months[0]。給列表一個數字，它將返回儲存在該位置的值。
語句 if 1 <= which_one <= 12: 只有在 which_one 包含在 1 到 12 之間時才為真（換句話說，如果您在代數中見過它，就會像您預期的那樣）。
可以將列表看作是一系列盒子。每個盒子都有不同的值。例如，由 demolist = ['life', 42, 'the universe', 6, 'and', 9] 建立的盒子將如下所示
| 盒子編號 | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| demolist | "life" | 42 | "the universe" | 6 | "and" | 9 |
每個盒子都透過其編號來引用，因此語句 demolist[0] 將獲取 'life'，demolist[1] 將獲取 42，依此類推，直到 demolist[5] 獲取 9。
以下示例只是為了展示列表可以執行的其他許多操作（這次我不希望您鍵入它，但您可能需要玩玩列表，直到您對它們感到滿意）。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
輸出是
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式。請注意，您可以直接 print 整個列表。接下來，append 函式用於在列表末尾新增一個新專案。len 返回列表中包含的專案數。列表的有效索引（如在 [] 內使用的數字）範圍為 0 到 len - 1。index 函式告訴專案在列表中的第一個位置在哪裡。請注意 demolist.index(42) 返回 1，而 demolist[1] 執行時返回 42。行 # Next we will loop through the list 只是對程式設計師的提醒（也稱為註釋）。Python 將忽略以 # 開頭的任何行。接下來，以下幾行
c = 0
while c < len(demolist):
print 'demolist[', c, '] =', demolist[c]
c = c + 1
建立一個變數 c，它從 0 開始，並不斷遞增，直到達到列表的最後一個索引。同時，print 語句打印出列表中的每個元素。del 命令可用於刪除列表中的給定元素。接下來的幾行使用 in 運算子來測試元素是否在列表中或不在列表中。sort 函式對列表進行排序。如果您需要按從小到大或按字母順序排序的列表，這將很有用。請注意，這會重新排列列表。總之，對於列表，會發生以下操作
| 示例 | 解釋 |
|---|---|
demolist[2]
|
訪問索引 2 處的元素 |
demolist[2] = 3
|
將索引 2 處的元素設定為 3 |
del demolist[2]
|
刪除索引 2 處的元素 |
len(demolist)
|
返回 demolist 的長度 |
"value" in demolist
|
如果為 True，則"value"是 demolist 中的元素 |
"value" not in demolist
|
如果 "value" 不是 demolist 中的元素，則為 True |
demolist.sort()
|
對 demolist 進行排序 |
demolist.index("value")
|
返回 "value" 第一次出現的索引 |
demolist.append("value")
|
在列表末尾新增一個元素 "value" |
demolist.remove("value")
|
從 demolist 中刪除 value 的第一次出現（與 del demolist[demolist.index("value")] 相同） |
以下示例以更有用的方式使用這些功能
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"
以下是部分輸出
-------------------- 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
這是一個很長的程式。讓我們看一下原始碼。行 namelist = [] 使變數 namelist 成為一個沒有專案（或元素）的列表。下一行重要的程式碼是 while menu_item != 9:。此行啟動一個迴圈，該迴圈允許此程式的菜單系統。接下來的幾行顯示一個選單，並決定要執行程式的哪個部分。
部分程式碼
current = 0
if len(namelist) > 0:
while current < len(namelist):
print current, ".", namelist[current]
current = current + 1
else:
print "List is empty"
遍歷列表並列印每個名稱。len(namelist) 告訴列表中包含多少個專案。如果 len 返回 0，則列表為空。
然後，在幾行之後，出現語句 namelist.append(name)。它使用 append 函式在列表末尾新增一個專案。向下跳兩行，請注意這段程式碼
item_number = namelist.index(del_name)
del namelist[item_number]
在這裡，index 函式用於查詢稍後將用於刪除專案的索引值。del namelist[item_number] 用於刪除列表的元素。
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 查詢 item_number，然後將 new_name 放在 old_name 所在的位置。
恭喜您，現在您已經掌握了列表，您已經足夠了解該語言，可以執行計算機可以執行的任何計算（這在技術上被稱為圖靈完備性）。當然，還有許多功能可以使您的生活更輕鬆。
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 分別指向 1 和 0。它們通常用於健全性檢查、迴圈條件等。您將在稍後（章節 布林表示式）瞭解有關此內容的更多資訊。
示例輸出
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
擴充套件 test.py 程式，使其有一個選單，提供進行測試、檢視問題和答案列表以及退出選項。此外，新增一個新的問題，詢問“真正的先進機器發出什麼聲音？”，答案是“ping”。
解決方案
擴充套件 test.py 程式，使其有一個選單，提供進行測試、檢視問題和答案列表以及退出選項。此外，新增一個新的問題，詢問“真正的先進機器發出什麼聲音？”，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: ")