python --- 列表

用下标取得列表中的单个值

>>> spam = ['cat','bat','rat','elephant']>>> spam[0]'cat'>>> spam[1]'bat'>>> spam[2]'rat'>>> spam[3]'elephant'>>> ['cat','bat','rat','elephant'][3]'elephant'>>> 'hello' + spam[0]'hellocat'>>> 'the ' + spam[1] + 'ate the ' + spam[0] + '.''the batate the cat.'

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负数下标

>>> 'the ' + spam[1] + 'ate the ' + spam[0] + '.''the batate the cat.'>>> spam = ['cat','bat','rat','elephant']>>> spam[-1]'elephant'>>> spam[-3]'bat'>>> 'the ' + spam[-1] + 'is afraid of the ' + spam[-3] + '.''the elephantis afraid of the bat.'

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利用切片取得子列表

>>> spam = ['cat', 'bat','rat','elephant']>>> spam[0:4]['cat', 'bat', 'rat', 'elephant']>>> spam[1:3]['bat', 'rat']>>> spam[0:-1]['cat', 'bat', 'rat']

作为快捷方法，可以省略切片中冒号两边的一个下标或两个下标。

>>> spam = ['cat','bat','rat','elephant']>>> spam[:2]['cat', 'bat']>>> spam[1:]['bat', 'rat', 'elephant']>>> spam[:]['cat', 'bat', 'rat', 'elephant']

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用len()取得列表长度

>>> spam = ['cat','bat','rat']>>> len(spam)3

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用下标改变列表中的值

>>> spam = ['cat','bat','rat','elephant']>>> spam[1]='aardvark'>>> spam['cat', 'aardvark', 'rat', 'elephant']>>> spam[2] = spam[1]>>> spam['cat', 'aardvark', 'aardvark', 'elephant']>>> spam[-1] = 123>>> spam['cat', 'aardvark', 'aardvark', 123]

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列表连接和列表复制

>>> [1,2,3] + ['a','b','c'][1, 2, 3, 'a', 'b', 'c']>>> ['a','b','c']*3['a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c']>>> spam = [1,2,3]>>> spam = spam + ['a','b','c']>>> spam[1, 2, 3, 'a', 'b', 'c']

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用del语句从列表中删除值

>>> spam = ['cat','bat','rat','elephant']>>> del spam[2]>>> spam['cat', 'bat', 'elephant']>>> del spam[2]>>> spam['cat', 'bat']

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使用列表

myNumber = []while True:    print('输入第'+str(len(myNumber)+1) +'变量'  )    name = input()    '''等于空退出循环'''    if name == '':        break    '''连接复制列表到变量'''    myNumber = myNumber + [name]print('总共输入的变量是:'+ str(len(myNumber)) + '个')for name in myNumber:    print(name)

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列表用于循环

for i in range(4):    print(i)for a in [0,1,2,3]:    print(a)spam = ['cat','bat','rat','elephant']for b in range(len(spam)):    print('下标是'+ str(b) + '对应值是' + spam[b])

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in 和 not in操作符

>>> 'howdy' in ['hello','hi','howdy','heyas']True>>> spam = ['hello','hi','howdy','heyas']>>> 'cat' in spamFalse>>> 'howdy' not in spamFalse>>> 'cat' not in spamTrue

让程序判断名字在不在列表中

myPets = ['Zophie','Pooka','Fat-tail']print('输入名字')name = input()if name not in myPets:    print('输入的名字' + name + '不在列表中')else:    print(name + '在列表中')

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多重复制技巧

>>> cat = ['fat','black','loud']>>> size = cat[0]>>> color = cat[1]>>> disposition = cat[2]>>> print(size,color,disposition)fat black loud>>> # 多重赋值技巧是一种快捷方式>>> cat = ['fat','black','loud']>>> size,color,disposition = cat>>> print(size,color,disposition)fat black loud>>> # 变量的数目和列表的长度必须严格相等，否则python将给出ValueError

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增强的赋值操作

>>> spam = spam + 1>>> spam43>>> spam = 42>>> spam += spam>>> spam84>>> spam = 42>>> spam += 1>>> spam43>>> spam = 'hello'>>> spam += 'world!'>>> spam'helloworld!'>>> bacon = ['cat']>>> bacon *= 3>>> bacon['cat', 'cat', 'cat']

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用index()方法在列表中查找值

>>> spam = ['hello','hi','howdy','heyas']>>> spam.index('hello')0>>> spam.index('heyas')3>>> spam = ['cat','cat','cat','cat']>>> spam.index('cat')0>>> # 出现列表中重复的值，就返回它第一个出现的下标

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用append()和insert()方法在列表中添加值

>>> spam = ['cat','dog','bat']>>> spam.append('moose')>>> spam['cat', 'dog', 'bat', 'moose']>>> # insert()方法可以在列表任意下标处插入一个值>>> spam = ['cat','dog','bat']>>> spam.insert(1,'hello')>>> spam['cat', 'hello', 'dog', 'bat']>>> spam.insert(-1,'rat')>>> spam['cat', 'hello', 'dog', 'rat', 'bat']

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用remove()方法从列表中删除值

>>> spam = ['cat','bat','rat','elephant']>>> spam.remove('bat')>>> spam['cat', 'rat', 'elephant']>>> # 列表中出现多次，只有第一次出现的值会被删除。>>> spam = ['cat','cat','cat']>>> spam.remove('cat')>>> spam['cat', 'cat']

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用sort()方法将列表中的值排序

spam = [2,4,2.3,8,-8,-2.3]>>> spam.sort()>>> spam[-8, -2.3, 2, 2.3, 4, 8]>>> spam = ['a','e','d','b','c']>>> spam.sort()>>> spam['a', 'b', 'c', 'd', 'e']>>> # reverse 关键字参数为True,让sor按逆序排序。>>> spam.sort(reverse=True)>>> spam['e', 'd', 'c', 'b', 'a']>>> # 不能对既有数字又有字符串值的列表排序>>> spam = [1,5,7,'adf','adsfd']>>> spam.sort()Traceback (most recent call last):  File "<input>", line 1, in <module>TypeError: unorderable types: str() < int()>>> # sort()方法对字符串排序时，使用'ASCII'字符顺序>>> spam = ['Alice','abcd','BOb','badgers','Cloor','name']>>> spam.sort()>>> spam['Alice', 'BOb', 'Cloor', 'abcd', 'badgers', 'name']>>> # 如果需要按照普通的字典顺序来排序，就在sort()方法调用时，将关键字参数key设置为str.lower>>> spam = ['a','z','A','Z']>>> spam.sort(key=str.lower)>>> spam['a', 'A', 'z', 'Z']

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例子程序： 神奇8球和列表

import randommessages = [    'It is certain',    'It is decidedly so',    'Yes definitely',    'Reply hazy try again',    'Ask again later',    'Concentrate and ask again',    'My reply is no',    'Outlook not so good',    'Very doubtful']print(messages[random.randint(0,len(messages) -1 )])

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类似列表的类型：字符串和元组

>>> name = 'Zophie'>>> name[0]'Z'>>> name[-2]'i'>>> name[:4]'Zoph'>>> 'Zo' in nameTrue>>> 'z' in nameFalse>>> 'p' not in nameFalse>>> for i in name:...     print(i)...     Zophie

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可变和不可变数据类型

列表是‘可变的’
字符串 ‘是不可变的’

>>> name = 'Zophie a cat'>>> name[7] = 'aaa'Traceback (most recent call last):  File "<input>", line 1, in <module>TypeError: 'str' object does not support item assignment>>> name = 'Zophoe a cat'>>> newName = name[0:7] + 'aaa' + name[8:12]>>> name'Zophoe a cat'>>> newName'Zophoe aaa cat'>>> eggs = [1,2,3]>>> eggs = [4,5,6]>>> eggs[4, 5, 6]>>> eggs = [1,2,3]>>> del eggs[2]>>> del eggs[1]>>> del eggs[0]>>> eggs.append(7)>>> eggs.append(8)>>> eggs.append(9)>>> eggs[7, 8, 9]

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元组数据类型

>>> eggs = ('hello',42, 0.5)>>> eggs[0]'hello'>>> eggs[1:3](42, 0.5)>>> len(eggs)3>>> eggs = ('hello',88, 2.22)>>> eggs[1]=99Traceback (most recent call last):  File "<input>", line 1, in <module>TypeError: 'tuple' object does not support item assignment>>> type(('hello',))<class 'tuple'>>>> type(('hello'))<class 'str'>

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用list()和tuple()函数来转换类型

>>> tuple(['cat','name',2,3.14])('cat', 'name', 2, 3.14)>>> list(('cat','name',2,3.14))['cat', 'name', 2, 3.14]

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引用

>>> spam = 42>>> cheese = spam>>> spam = 100>>> spam100>>> cheese42>>> spam = [0,1,2,3,4,5]>>> cheese = spam>>> cheese[1] = 'hello'>>> spam[0, 'hello', 2, 3, 4, 5]>>> cheese[0, 'hello', 2, 3, 4, 5]

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传递引用

def eggs(name):    name.append('hello')spam = [1,2,3]eggs(spam)print(spam)

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copy模块的copy()和deepcopy()函数

>>> import copy>>> spam = ['a','b','c','d']>>> cheese = copy.copy(spam)>>> spam['a', 'b', 'c', 'd']>>> cheese['a', 'b', 'c', 'd']>>> cheese[1]= 88>>> cheese['a', 88, 'c', 'd']>>> name = [[1,2,3],['a','b','c']]>>> cheese = copy.deepcopy(name)>>> cheese[1][0] = 'aaa'>>> name[[1, 2, 3], ['a', 'b', 'c']]>>> cheese[[1, 2, 3], ['aaa', 'b', 'c']]