Python基础2 之2

参考地址：https://www.cnblogs.com/alex3714/articles/5717620.html

字符串操作

>>> line = "my name is liaowei ."
#首字母大写
>>> line.capitalize()
'My name is liaowei .'
>>> line
#大写全部变小写
>>> line.casefold()
'my name is liaowei .'

#局中显示
>>> line.center(40," ")
'          my name is liaowei .          '
>>> line.center(40,"-")
'----------my name is liaowei .----------'
#计算子串的个数
>>> line.count("i")
3
#转为byte类型
>>> line.encode()
b'my name is liaowei .'
#判断一什么结尾
>>> line.endswith(".")
True
>>> line.endswith("  ")
False
#将\t转为多少个空格
>>> "liaowei\tshihaoren"
'liaowei\tshihaoren'
>>> "liaowei\tshihaoren".expandtabs(10)
'liaowei   shihaoren'
>>> "liaowei\tshihaoren".expandtabs(20)
'liaowei             shihaoren'
>>> "liaowei\tshihaoren".expandtabs(1)
'liaowei shihaoren'
#查找子串
>>> line.find("A")
-1
>>> line.find("i")
8

#返回子串的索引
>>> line
'my name is liaowei .'
>>> line.index("i")
8
#format
>>> "__1.{}___2.{}__".format("a")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: tuple index out of range
>>> "__1.{}___2.{}__".format("a",2)
'__1.a___2.2__'
>>> "__1.{0}___2.{0}__".format("a",2)
'__1.a___2.a__'
>>> "__1.{}___2.{}__".format("a",2, 3)
'__1.a___2.2__'
>>> "__1.{one}___2.{two}__".format("a",2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'one'
>>> "__1.{one}___2.{two}__".format(one="a",two=2)
'__1.a___2.2__'
>>> "__1.{one}___2.{two}__".format()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'one'
>>> "__1.{one}___2.{two}__".format(one="a")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'two'
>>> "__1.{one}___2.{two}__".format_map("one":"a","two":2)
  File "<stdin>", line 1
    "__1.{one}___2.{two}__".format_map("one":"a","two":2)
                                            ^
SyntaxError: invalid syntax
>>> "__1.{one}___2.{two}__".format_map({"one":"a","two":2})
'__1.a___2.2__'
>>> "123".isdigit()
True
>>> "123a".isdigit()
False
>>> "123a".isnumeric()
False
>>> "123".isnumeric()
True
>>> "123.01".isnumeric()
False
>>> "123".isspace()
False
>>> "  ".isspace()
True
>>> "    \n\t\r ".isspace()
True
>>> "My name is".istitle()
False
>>> "My Name Is".istitle()
True
>>> "My Name Is".isupper()
False
>>> "ABC".isupper()
True
>>> "ABC ".isupper()
True
>>> "ABC 123".isupper()
True
>>> "ABC 123a".isupper()
False
#join
>>> "!".join(['alex','jack','rain'])
'alex!jack!rain'
>>> "".join(['alex','jack','rain'])
'alexjackrain'
>>> "@@@".join(['alex','jack','rain'])
'alex@@@jack@@@rain'

#maketrans
>>> intab = "aeiou"
>>> outtab = "12345" 
>>> trantab = str.maketrans(intab, outtab)
>>> str = "this is string example....wow!!!"
>>> str.translate(trantab)
'th3s 3s str3ng 2x1mpl2....w4w!!!'
#partition
>>> "my name is liaowei".partition("is")
('my name ', 'is', ' liaowei')
>>> "my name is liaowei".partition("i")
('my name ', 'i', 's liaowei')
>>> "my name is liaowei".partition("m")
('', 'm', 'y name is liaowei')
>>> "my name is liaowei".partition("na")
('my ', 'na', 'me is liaowei')
>>> "my name is liaowei".partition("name")
('my ', 'name', ' is liaowei')
#大小写互换
>>> "My name is liaowei".swapcase()
'mY NAME IS LIAOWEI'
#填0
>>> "My name is liaowei".zfill(20)
'00My name is liaowei'
>>> "My name is liaowei".zfill(30)
'000000000000My name is liaowei'

#从左向右填充
>>> "My name is liaowei".ljust(40 ,"-")
'My name is liaowei----------------------'

#从右向左填充
>>> "My name is liaowei".rjust(40 ,"-")
'----------------------My name is liaowei'
>>> "My name is liaowei".rjust(3 ,"-")
'My name is liaowei'
>>> "My name is liaowei".rjust(100 ,"-")
'----------------------------------------------------------------------------------My name is liaowei'
>>> "My name is liaowei".rjust(14 ,"-")
'My name is liaowei'
>>> "My name is liaowei".rjust(20 ,"-")
'--My name is liaowei'

#检测一段字符串可否被当作标志符，即是否符合变量命名规则
>>> "My name is liaowei".isidentifier()
False
>>> "for".isidentifier()
True
>>> "while".isidentifier()
True
>>> "a".isidentifier()
True
>>> "in".isidentifier()
True
>>> "if".isidentifier()
True

 字典

　　特点：无须的，key是唯一的。

#增加
>>> info = {}
>>> info["name"] = "liaowei"
>>> info
{'name': 'liaowei'}

#修改
>>> info
{'name': 'liaowei'}
>>> info["name"] = "abcdefg"
>>> info
{'name': 'abcdefg'}

#删除
>>> info = {'name':'liaowei','surname':'liao'}
>>> info.pop("surname")
'liao'
>>> del info["name"]
>>> info
{}

#查找
>>> info = {'name':'liaowei','surname':'liao'}
>>> info.get('name')
'liaowei'
>>> info['name']
'liaowei'
>>> info['name1'] #当字典里没有时会报错
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'name1'
>>> info.get('name1') #当字典里没有时不会报错

#其他
>>> info.values()
dict_values(['liaowei', 'liao'])
>>> info.keys()
dict_keys(['name', 'surname'])
>>> info.items()
dict_items([('name', 'liaowei'), ('surname', 'liao')])

>>> info.setdefault('name', 'abcdef')
'liaowei'
>>> info
{'name': 'liaowei', 'surname': 'liao'}
#update
>>> info
{'name': 'liaowei', 'surname': 'liao'}
>>> b={1:2,'name':'abcdef'}
>>> info.update(b)
>>> info
{1: 2, 'name': 'abcdef', 'surname': 'liao'}

#一个列表生成默认字典
>>> dict.fromkeys([1,2,3],'testd')
{1: 'testd', 2: 'testd', 3: 'testd'}