基礎(chǔ)小函數(shù)、字符串函數(shù)、序列函數(shù)

序列、元組、列表小函數(shù)

max() 求最大值(列表、元組、序列)

min() 求最小值

len() 求長度

>>> a = [1,2,3,4]

>>> max(a)

4

>>> min(a)

1

>>> len(a)

4

>>>

運算小函數(shù)

divmod() 求運算模，返回一個元組，第一個參數(shù)是商，第二個是余數(shù)

pow(x,y) 指數(shù)運算，x的y次方

pow(x,y,z) x的y次方，在與z取模

round() 浮點數(shù)

>>> a = 3

>>> b = 4

>>> divmod(a,b)

(0, 3)

>>> divmod(b,a)

(1, 1)

>>> pow(a,b)

81

>>> pow(a,b,8)

1

>>>

>>> a/b

0.75

>>> round(a/b)

1

>>> round(a/b,2)

0.75

>>> round(a/b,4)

0.75

>>>

其它小函數(shù)

callable() 測試函數(shù)是否可被調(diào)用

isinstance(l,list) 測試l是否是一個list

>>> def f(x):

pass

>>> callable(fc)

Traceback (most recent call last):

File "", line 1, in

callable(fc)

NameError: name 'fc' is not defined

>>> callable(f)

True

>>>

>>> l = [1,2,3,4]

>>> t = (2,3,4,5)

>>> s = 'hello'

>>> isinstance(l,list)

True

>>> isinstance(t,tuple)

True

>>> isinstance(s,str)

True

>>> isinstance(l,str)

False

字符串函數(shù)

str.capitalize() 首字母大寫

str.replace('x','y',count) 字符串替換 count 替換幾次

str.split(“”，sep) 將字符串轉(zhuǎn)換為列表，用“”切割，sep切割幾次

>>> str1 = 'hello world , today is very good day'

>>> str1.capitalize()

'Hello world , today is very good day'

>>> str1

'hello world , today is very good day'

>>> str1.replace('o','9',1)

'hell9 world , today is very good day'

>>> str1.replace('o','9',3)

'hell9 w9rld , t9day is very good day'

>>> str1.replace('o','9')

'hell9 w9rld , t9day is very g99d day'

>>>

>>> ip = '192.168.1.254'

>>> ip.split(".")

['192', '168', '1', '254']

>>> ip.split(".",1)

['192', '168.1.254']

>>>

序列函數(shù)

filter() 過濾函數(shù)

filter(f,l) 將l列表中的值傳給函數(shù)f進行判斷，保留滿足要求的數(shù)值 函數(shù)return True

zip() 將兩個列表的值進行對應(yīng)，以元組存放在列表中。以最短的為組合數(shù)

map(None,a,b) 將列表a、b的值對應(yīng)起來傳給None函數(shù)，None可以作為函數(shù)

fc(x,y)

reduce(fc,list) 將列表list的值依次傳輸給函數(shù)fc

>>> def f(x):

if x>5:

return True

>>> l = [1,2,3,5,6,2,3,6,7,8]

>>> filter(f,l)

>>> list(filter(f,l))

[6, 6, 7, 8]

>>>

>>> name = ['zhang','li','wang','zhou']

>>> age = [22,21,23,24]

>>> list(zip(name,age))

[('zhang', 22), ('li', 21), ('wang', 23), ('zhou', 24)]

>>> city = ['beijing','shanxi','xinjiang']

>>> list(zip(name,age,city))

[('zhang', 22, 'beijing'), ('li', 21, 'shanxi'), ('wang', 23, 'xinjiang')]

>>>

>>> def f(name,age):

return name,age

>>> list(map(f,name,age))

[('zhang', 22), ('li', 21), ('wang', 23), ('zhou', 24)]

>>>

>>> def f(x,y):

return x+y

>>> a = [1,2,3,4]

>>> b = [1,2,3,4]

>>> list(map(f,a,b))

[2, 4, 6, 8]

>>>

>>>

>>> l = range(100)

>>> reduce(f,l)

Traceback (most recent call last):

File "", line 1, in

reduce(f,l)

NameError: name 'reduce' is not defined

>>>

>>> from functools import reduce

>>> reduce(f,l)

4950

>>> l = range(101)

>>> reduce(f,l)

5050

>>>

>>>

使用reduce時需要導(dǎo)入相應(yīng)的模塊。

reduce用來計算階乘很方便。根據(jù)reduce，可以寫成一行代碼來。

>>> n = 101

>>> range(n)

range(0, 101)

>>> reduce(lambda x,y:x+y , l)

5050

>>>

+修改為*，就是求n的階乘了。不對n-1的階乘。

小例子動手寫一下，印象更深刻。

讀書和健身總有一個在路上

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