字符串常用函数

1 字符串创建：var1 = 'Hello World!'

2 字符串不可变

3 单字符也在Python也是作为一个字符串使用

4 Python 访问子字符串，可以使用方括号来截取字符串

var1 = 'Hello World!'
var2 = "Runoob"
print ("var1[0]: ", var1[0])
print ("var2[1:5]: ", var2[1:5])

5 字符串转义：在需要在字符中使用特殊字符时，python用反斜杠(\)转义字符

6 字符串运算

+ 字符串连接

* 重复输出字符串

[] 通过索引取字符串中字符

[:] 截取字符串中部分字符

in 如果字符串中包含给定字符则返回true

not in 如果字符串中不包含给定字符则返回true

r/R 原始字符串 - 原始字符串：所有的字符串都是直接按照字面的意思来使用，没有转义特殊或不能打印的字符。 原始字符串除在字符串的第一个引号前加上字母"r"（可以大小写）以外，与普通字符串有着几乎完全相同的语法。

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 判断从控制台输入的字符串是否是数字

str = input("please input the number:")

if str.isdigit():

为True表示输入的所有字符都是数字，否则，不是全部为数字

str为字符串 str.isalnum() 所有字符都是数字或者字母 str.isalpha() 所有字符都是字母 str.isdigit() 所有字符都是数字 str.islower() 所有字符都是小写 str.isupper() 所有字符都是大写 str.istitle() 所有单词都是首字母大写，像标题 str.isspace() 所有字符都是空白字符、\t、\n、\r

 

 

https://www.cnblogs.com/rollenholt/archive/2011/11/25/2263722.html

>>> import string
>>> string.ascii_letters
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> string.ascii_lowercase
'abcdefghijklmnopqrstuvwxyz'
>>> string.ascii_uppercase
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> string.digits
'0123456789'
>>> string.hexdigits
'0123456789abcdefABCDEF'
>>> string.letters
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
>>> string.lowercase
'abcdefghijklmnopqrstuvwxyz'
>>> string.uppercase
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> string.octdigits
'01234567'
>>> string.punctuation
'!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~'
>>> string.printable
'0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\x0b\x0c'
>>> string.whitespace
'\t\n\x0b\x0c\r
　


>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
>>> '{}, {}, {}'.format('a', 'b', 'c')  # 2.7+ only
'a, b, c'
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc')      # unpacking argument sequence
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad')   # arguments' indices can be repeated
'abracadabra'
 
>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)
'Coordinates: 37.24N, -115.81W'
 
>>> c = 3-5j
>>> ('The complex number {0} is formed from the real part {0.real} '
...  'and the imaginary part {0.imag}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point(object):
...     def __init__(self, x, y):
...         self.x, self.y = x, y
...     def __str__(self):
...         return 'Point({self.x}, {self.y})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)
 
>>> coord = (3, 5)
>>> 'X: {0[0]};  Y: {0[1]}'.format(coord)
'X: 3;  Y: 5'
 
>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"
 
>>> '{:<30}'.format('left aligned')
'left aligned                  '
>>> '{:>30}'.format('right aligned')
'                 right aligned'
>>> '{:^30}'.format('centered')
'           centered           '
>>> '{:*^30}'.format('centered')  # use '*' as a fill char
'***********centered***********'
 
>>> '{:+f}; {:+f}'.format(3.14, -3.14)  # show it always
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14)  # show a space for positive numbers
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14)  # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'
 
>>> # format also supports binary numbers
>>> "int: {0:d};  hex: {0:x};  oct: {0:o};  bin: {0:b}".format(42)
'int: 42;  hex: 2a;  oct: 52;  bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}".format(42)
'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'
 
>>> '{:,}'.format(1234567890)
'1,234,567,890'
 
>>> points = 19.5
>>> total = 22
>>> 'Correct answers: {:.2%}.'.format(points/total)
'Correct answers: 88.64%'
 
>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'
 
>>> for align, text in zip('<^>', ['left', 'center', 'right']):
...     '{0:{fill}{align}16}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12):
...     for base in 'dXob':
...         print '{0:{width}{base}}'.format(num, base=base, width=width),
...     print
...
    5     5     5   101
    6     6     6   110
    7     7     7   111
    8     8    10  1000
    9     9    11  1001
   10     A    12  1010
   11     B    13  1011
 
>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
'tim likes kung pao'
>>> d = dict(who='tim')
>>> Template('Give $who $100').substitute(d)
Traceback (most recent call last):
[...]
ValueError: Invalid placeholder in string: line 1, col 10
>>> Template('$who likes $what').substitute(d)
Traceback (most recent call last):
[...]
KeyError: 'what'
>>> Template('$who likes $what').safe_substitute(d)
'tim likes $what'
　

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string.capitalize(word) 返回一个副本，首字母大写
>>> string.capitalize("hello")
'Hello'
>>> string.capitalize("hello world")
'Hello world'
 
>>> string.split("asdadada asdada")
['asdadada', 'asdada']
 
>>> string.strip("              adsd         ")
'adsd'
>>> string.rstrip("              adsd         ")
'              adsd'
>>> string.lstrip("              adsd         ")
'adsd         '
 
string.swapcase(s) 小写变大写，大写变小写
>>> string.swapcase("Helloo")
'hELLOO'
 
>>> string.ljust("ww",20)
'ww                  '
>>> string.rjust('ww',20)
'                  ww'
>>> string.center('ww',20)
'         ww         '
string.zfill(s, width)
Pad a numeric string on the left with zero digits until the given width is reached. Strings starting with a sign are handled correctly.
>>> string.zfill('ww',20)
'000000000000000000ww'