小甲鱼教学笔记——列表：常用操作符、字符串格式化、序列

1. 列表：常用操作符

list1=[123]
list2=[234]
list1>list2

False

list1=[1,2,3]
list2=[2,3,4]
list1>list2

False

list3=[1,2,3]
(list1<list2)and(list1==list3)

True

list4=list1+list2
list4

[1, 2, 3, 2, 3, 4]

list1*3

[1, 2, 3, 1, 2, 3, 1, 2, 3]

list3=[1,2,3]
list3*=3

list3

[1, 2, 3, 1, 2, 3, 1, 2, 3]

1 in list3

True

'yuhongxia' not in list3

True

list5=[123,['余红霞','最漂亮'],456]
'余红霞'in list5

False

'余红霞'in list5[1]

True

dir(list)#列表的所有方法

['__add__',
 '__class__',
 '__contains__',
 '__delattr__',
 '__delitem__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__getitem__',
 '__gt__',
 '__hash__',
 '__iadd__',
 '__imul__',
 '__init__',
 '__init_subclass__',
 '__iter__',
 '__le__',
 '__len__',
 '__lt__',
 '__mul__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__reversed__',
 '__rmul__',
 '__setattr__',
 '__setitem__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'append',
 'clear',
 'copy',
 'count',
 'extend',
 'index',
 'insert',
 'pop',
 'remove',
 'reverse',
 'sort']

list3.count(1)

3

list3.index(1)

0

list3.index(1,2,5)

3

list3.reverse()
list3

[3, 2, 1, 3, 2, 1, 3, 2, 1]

list6=[4,5,6,2,1,8]
list6.sort()
list6

[1, 2, 4, 5, 6, 8]

list6.sort(reverse=True)

list6

[8, 6, 5, 4, 2, 1]

2. 字符串格式化

• format():位置参数、关键字参数
• {}表示replacement字段

"{0} love {1}.{2}".format("i","china","com")

'i love china.com'

"{a} love {b}.{c}".format(a="I",b="china",c="com")

'I love china.com'

"{0} love {b}.{c}".format("I",b="china",c="com")

'I love china.com'

"{{0}}".format("不打印，因为0已经被解释掉了")

'{0}'

"{0:.1f}.{1}".format(27.658,"GB")#:.1f表示保留一位小数

'27.7.GB'

%c:格式化字符及ASCII码

"%c" % 97

'a'

'%c %c %c' % (97,98,99)

'a b c'

%s:格式化字符串

"%s" % "i love china"

'i love china'

%d:格式化整数

'%d + %d = %d' % (4,5,4+5)

'4 + 5 = 9'

'%o' % 10

'12'

'%x' % 10

'a'

'%X' % 10

'A'

'%f' % 27.658

'27.658000'

'%.2f' % 27.658999

'27.66'

'%e' % 27.658999

'2.765900e+01'

'%g' % 27.658999

'27.659'

格式化操作辅助指令：

'%6.1f' % 27.658999

'  27.7'

'%.2e' % 27.658999

'2.77e+01'

'%10d'% 10

'        10'

'%-10d'% 10

'10        '

'%+d'% 10

'+10'

'%+d'% -10

'-10'

'%#o' % 10

'0o12'

'%#x' % 10

'0xa'

'%010d'% 10

'0000000010'

字符串转义字符含义：

3. 序列：列表、元组和字符串

列表、元组和字符串的共同特点：

• 都可以通过索引得到每一个元素
• 默认索引值总是从0开始
• 可以通过分片的方法得到一个范围
• 有很多共同的操作符（重复操作符、拼接操作符、成员关系操作符）

list（）：把一个可迭代对象转换为列表

a=list()
a

[]

b="I love china"
b=list(b)
b

['I', ' ', 'l', 'o', 'v', 'e', ' ', 'c', 'h', 'i', 'n', 'a']

c=(1,1,2,3,5,8,13,21,34)
c=list(c)
c

[1, 1, 2, 3, 5, 8, 13, 21, 34]

tuple():把一个可迭代对象转换为元组

help(tuple)

Help on class tuple in module builtins:

class tuple(object)
 |  tuple(iterable=(), /)
 |  
 |  Built-in immutable sequence.
 |  
 |  If no argument is given, the constructor returns an empty tuple.
 |  If iterable is specified the tuple is initialized from iterable's items.
 |  
 |  If the argument is a tuple, the return value is the same object.
 |  
 |  Methods defined here:
 |  
 |  __add__(self, value, /)
 |      Return self+value.
 |  
 |  __contains__(self, key, /)
 |      Return key in self.
 |  
 |  __eq__(self, value, /)
 |      Return self==value.
 |  
 |  __ge__(self, value, /)
 |      Return self>=value.
 |  
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |  
 |  __getitem__(self, key, /)
 |      Return self[key].
 |  
 |  __getnewargs__(self, /)
 |  
 |  __gt__(self, value, /)
 |      Return self>value.
 |  
 |  __hash__(self, /)
 |      Return hash(self).
 |  
 |  __iter__(self, /)
 |      Implement iter(self).
 |  
 |  __le__(self, value, /)
 |      Return self<=value.
 |  
 |  __len__(self, /)
 |      Return len(self).
 |  
 |  __lt__(self, value, /)
 |      Return self<value.
 |  
 |  __mul__(self, value, /)
 |      Return self*value.
 |  
 |  __ne__(self, value, /)
 |      Return self!=value.
 |  
 |  __repr__(self, /)
 |      Return repr(self).
 |  
 |  __rmul__(self, value, /)
 |      Return value*self.
 |  
 |  count(self, value, /)
 |      Return number of occurrences of value.
 |  
 |  index(self, value, start=0, stop=9223372036854775807, /)
 |      Return first index of value.
 |      
 |      Raises ValueError if the value is not present.
 |  
 |  ----------------------------------------------------------------------
 |  Static methods defined here:
 |  
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.

str(obj):把obj对象转换为字符串

str(123)

'123'

其他

sorted(c)

[1, 1, 2, 3, 5, 8, 13, 21, 34]

reversed(c)

<list_reverseiterator at 0x13a5b945788>

list(reversed(c))

[34, 21, 13, 8, 5, 3, 2, 1, 1]

enumerate(c)

<enumerate at 0x13a5c86fae8>

list(enumerate(c))

[(0, 1), (1, 1), (2, 2), (3, 3), (4, 5), (5, 8), (6, 13), (7, 21), (8, 34)]

a=[1,2,3,4,5,6,7,8]
b=[3,4,5,6,7,8]
list(zip(a,b))

[(1, 3), (2, 4), (3, 5), (4, 6), (5, 7), (6, 8)]