Python中的多個(gè)內(nèi)置函數(shù)舉例

Python內(nèi)置函數(shù)：

成都創(chuàng)新互聯(lián)公司專(zhuān)業(yè)為企業(yè)提供資中網(wǎng)站建設(shè)、資中做網(wǎng)站、資中網(wǎng)站設(shè)計(jì)、資中網(wǎng)站制作等企業(yè)網(wǎng)站建設(shè)、網(wǎng)頁(yè)設(shè)計(jì)與制作、資中企業(yè)網(wǎng)站模板建站服務(wù)，十年資中做網(wǎng)站經(jīng)驗(yàn)，不只是建網(wǎng)站，更提供有價(jià)值的思路和整體網(wǎng)絡(luò)服務(wù)。

官方幫助文檔：

https://docs.python.org/2.7/

返回?cái)?shù)字的絕對(duì)值.

def fun(x):

if x < 0:

return -x

return x

print fun(10)
常用函數(shù)：

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()

是否是可調(diào)用對(duì)象

>>> a = 123

>>> callable(a)

False

>>> def a():

...     pass

...

>>> callable(a)

True

>>> class A(object):

...     pass

...

>>> callable(A)

True
type()

判斷類(lèi)型

>>> type(a)


isinstance()

判斷類(lèi)型,

>>> l =[1,2,3]

>>> isinstance(l,list)

True

>>> isinstance(l,str)

False

>>> isinstance(l,(list,str))

True

判斷是不是一個(gè)類(lèi)

>>> A



>>> a = A()

>>> a



>>> 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，不用時(shí)候不在內(nèi)存中產(chǎn)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()

轉(zhuǎn)換成復(fù)數(shù)

>>> 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()

變?yōu)?6進(jìn)制

>>> hex(10)

'0xa'

>>> hex(10L)

'0xaL'

>>> int(0xaL)

10
eval（）

把字符串當(dāng)成有效表達(dá)式求值。

>>> eval('0xaL')

10L

>>> eval("[1,23,'a']")

[1, 23, 'a']
oct()

10進(jìn)制轉(zhuǎn)成8進(jìn)制

>>> oct(10)

'012'

>>> oct(8)

'010'
chr()

查ASSIC碼對(duì)應(yīng)值:

>>> chr(97)

'a'

>>> chr(65)

'A'
ord()

>>> ord('A')

65
字符串處理的函數(shù)：

str.capitalize()

首字母變大寫(xiě)：

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'
序列處理函數(shù)：

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).

參數(shù)有幾個(gè)，函數(shù)里的參數(shù)也應(yīng)該對(duì)應(yīng)有幾個(gè)

>>> 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
列表表達(dá)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]