Python 内置函数:
官方帮助文档:
https://docs.python.org/2.7/
返回数字的绝对值.
- def fun(x):
- if x <0:
- return -x
- return x
- print fun(10)
常用函数:
- abs()
- >>> abs(-100)
- 100
取列表最大值和最小值
- max()
- >>> max('1235',123)
- '1235'
- min()
- >>> min('asdfq3w45')
- '3'
- len()
- >>> len('abcdf')
- 5
- >>> len([1,3,4,5])
- 4
- >>> len((1,3,4,5))
- 4
- >>> len({
- 1:3,2:5
- })
- 2
- divmod()
- >>> help(divmod)
- Help on built-in function divmod in module __builtin__:
- divmod(...)
- divmod(x, y) -> (quotient, remainder)
- Return the tuple (x//y, x%y). Invariant: div*y + mod == x.
- >>> divmod(5,2)
- (2, 1)
- pow()
- pow(...)
- pow(x, y[, z]) -> number
- With two arguments, equivalent to x**y. With three arguments,
- equivalent to (x**y) % z, but may be more efficient (e.g. for longs).
- >>> pow(2,3)
- 8
- >>> pow(2,3,3)
- 2
- round()
- round(...)
- round(number[, ndigits]) -> floating point number
- Round a number to a given precision in decimal digits (default 0 digits).
- This always returns a floating point number. Precision may be negative.
- >>> round(12.2)
- 12.0
- >>> round(12.23)
- 12.0
- >>> round(12.233,2)
- 12.23
- callable()
是否是可调用对象
- >>> a = 123
- >>> callable(a)
- False
- >>> def a():
- ... pass
- ...
- >>> callable(a)
- True
- >>> class A(object):
- ... pass
- ...
- >>> callable(A)
- True
- type()
判断类型
- >>> type(a)
- <type 'function'>
- isinstance()
判断类型,
- >>> l =[1,2,3]
- >>> isinstance(l,list)
- True
- >>> isinstance(l,str)
- False
- >>> isinstance(l,(list,str))
- True
判断是不是一个类
- >>> A
- <class 'A'>
- >>> a = A()
- >>> a
- <A object at 0x0379BE70>
- >>> isinstance(a,A)
- True
- cmp()
- >>> cmp(1,2)
- -1
- >>> cmp(1,0)
- 1
- >>> cmp(1,1)
- 0
- >>> cmp('a','ab')
- -1
- >>> cmp('a','a')
- 0
- >>> cmp('helloa','hello')
- 1
- range()
- >>> a = range(10)
- >>> a
- xrange()
效率更高, 不用时候不在内存中产生值
- [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
- >>> b = xrange(10)
- >>> b
- xrange(10)
- >>> for i in b:print i
- ...
- 0
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- int()
- >>> int(123.33)
- 123
- long()
- >>> long(200)
- 200L
- float()
- >>> float('123')
- 123.0
- >>> float('123.0022')
- 123.0022
- >>> float(123.0034)
- 123.0034
- >>> float(123)
- 123.0
- complex()
转换成复数
- >>> complex(123)
- (123+0j)
- >>> complex(3.1415926)
- (3.1415926+0j)
- str()
- >>> str('123')
- '123'
- list()
- >>> list('123')
- ['1', '2', '3']
- tuple()
- >>> tuple('123')
- ('1', '2', '3')
- hex()
变为 16 进制
- >>> hex(10)
- '0xa'
- >>> hex(10L)
- '0xaL'
- >>> int(0xaL)
- 10
- eval()
把字符串当成有效表达式求值.
- >>> eval('0xaL')
- 10L
- >>> eval("[1,23,'a']")
- [1, 23, 'a']
- oct()
10 进制转成 8 进制
- >>> oct(10)
- '012'
- >>> oct(8)
- '010'
- chr()
查 ASSIC 码对应值:
- >>> chr(97)
- 'a'
- >>> chr(65)
- 'A'
- ord()
- >>> ord('A')
- 65
字符串处理的函数:
str.capitalize()
首字母变大写:
- capitalize(...)
- S.capitalize() -> string
- Return a copy of the string S with only its first character
- capitalized.
- >>> s
- 'hello'
- >>> s.capitalize()
- 'Hello'
- str.replace()
- replace(...)
- S.replace(old, new[, count]) -> string
- Return a copy of string S with all occurrences of substring
- old replaced by new. If the optional argument count is
- given, only the first count occurrences are replaced.
- >>> s = 'hello,h'
- >>> s.replace('h','H')
- 'Hello,H'
- split()
- split(...)
- S.split([sep [,maxsplit]]) -> list of strings
- Return a list of the words in the string S, using sep as the
- delimiter string. If maxsplit is given, at most maxsplit
- splits are done. If sep is not specified or is None, any
- whitespace string is a separator and empty strings are removed
- from the result.
- >>> s = 'hello a\tb\nc'
- >>> s
- 'hello a\tb\nc'
- >>> s.split()
- ['hello', 'a', 'b', 'c']
- >> s
- 'hello a\tb\nc'
- >>> s.split(' ')
- ['hello', 'a\tb\nc']
- >>> s.split('\t')
- ['hello a', 'b\nc']
- >>> ip = '192.168.1.1'
- >>> ip.split('.')
- ['192', '168', '1', '1']
- >>> ip.split('.',1)
- ['192', '168.1.1']
- >>> ip.split('.',2)
- ['192', '168', '1.1']
- join()
- >>> range(10)
- [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
- >>> ''.join(str(i) for i in range(10))
- '0123456789'
- >>> int(''.join(str(i) for i in range(10)))
- 123456789
- string:
- import string
- string.lower
- >>> string.lower('Kfdfa')
- 'kfdfa'
- string.upper
- >>> string.upper('Kfdfa')
- 'KFDFA'
- string.capitalize()
- >>> string.capitalize('adfafgh')
- 'Adfafgh'
- string.replace()
- string.replace('afkgha','a','A')
- 'AfkghA'
序列处理函数:
- len()
- max()
- min()
- filter()
- filter(...)
- filter(function or None, sequence) -> list, tuple, or string
- Return those items of sequence for which function(item) is true. If
- function is None, return the items that are true. If sequence is a tuple
- or string, return the same type, else return a list.
- >>> filter(None,range(10))
- [1, 2, 3, 4, 5, 6, 7, 8, 9]
- >>> def f(x):
- ... if x % 2 == 0:
- ... return True
- ...
- >>> filter(f,range(10))
- [0, 2, 4, 6, 8]
- >>> filter(lambda x: x%2==0,range(10))
- [0, 2, 4, 6, 8]
- zip()
- zip(...)
- zip(seq1 [, seq2 [...]]) -> [(seq1[0], seq2[0] ...), (...)]
- Return a list of tuples, where each tuple contains the i-th element
- from each of the argument sequences. The returned list is truncated
- in length to the length of the shortest argument sequence.
- >>> a1 = [1,3,4]
- >>> a2 = ['a','b','c']
- >>> zip(a1,a2)
- [(1, 'a'), (3, 'b'), (4, 'c')]
- >>> dict(zip(a1,a2))
- {
- 1: 'a', 3: 'b', 4: 'c'
- }
- >>> dict(zip(a2,a1))
- {
- 'a': 1, 'c': 4, 'b': 3
- }
- >>> a3 = ['x','y','z']
- >>> zip(a1,a2,a3)
- [(1, 'a', 'x'), (3, 'b', 'y'), (4, 'c', 'z')]
- >>> zip(a1,a3)
- [(1, 'x'), (3, 'y'), (4, 'z')]
- >>> a3 = ['x','y']
- >>> zip(a1,a3)
- [(1, 'x'), (3, 'y')]
- >>> zip(a1,a2,a3)
- [(1, 'a', 'x'), (3, 'b', 'y')]
- map()
- map(...)
- map(function, sequence[, sequence, ...]) -> list
- Return a list of the results of applying the function to the items of
- the argument sequence(s). If more than one sequence is given, the
- function is called with an argument list consisting of the corresponding
- item of each sequence, substituting None for missing values when not all
- sequences have the same length. If the function is None, return a list of
- the items of the sequence (or a list of tuples if more than one sequence).
参数有几个, 函数里的参数也应该对应有几个
- >>> map(None,a1,a2,a3)
- [(1, 'a', 'x'), (3, 'b', 'y'), (4, 'c', None)]
- >>> def f(x):
- ... return x**2
- ...
- >>> map(f,a1)
- [1, 9, 16]
- >>> a1
- [1, 3, 4]
- >>> a1
- [1, 3, 4]
- >>> a2
- [2, 5, 6]
- >>> def f(x,y):
- ... return x*y
- ...
- >>> map(f,a1,a2)
- [2, 15, 24]
- >>> map(lambda x,y: x*y ,range(1,10),range(1,10))
- [1, 4, 9, 16, 25, 36, 49, 64, 81]
- reduce()
- reduce(...)
- reduce(function, sequence[, initial]) -> value
- Apply a function of two arguments cumulatively to the items of a sequence,
- from left to right, so as to reduce the sequence to a single value.
- For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates
- ((((1+2)+3)+4)+5). If initial is present, it is placed before the items
- of the sequence in the calculation, and serves as a default when the
- sequence is empty.
- >>> def f(x,y):
- ... return x + y
- ...
- >>> reduce(f,range(1,101))
- 5050
列表表达式:
- [i*2 for i in range(10)]
- >>> [i*2 for i in range(10)]
- [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
- >>> [i*2+10 for i in range(10)]
- [10, 12, 14, 16, 18, 20, 22, 24, 26, 28]
- [i*2+10 for i in range(10) if i%3 == 0]
- >>> [i*2+10 for i in range(10) if i%3 == 0]
- [10, 16, 22, 28]
来源: http://www.bubuko.com/infodetail-3118990.html