python常用內置函式使用-有解無憂

基礎小函式、字串函式、序列函式

序列、元組、串列小函式

max() 求最大值(串列、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
>>>

運算小函式
divmod() 求運算模，回傳一個元組，第一個引數是商，第二個是余數
pow(x,y) 指數運算，x的y次方
pow(x,y,z) x的y次方，在與z取模
round() 浮點數

>>> 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
>>>

其它小函式
callable() 測驗函式是否可被呼叫
isinstance(l,list) 測驗l是否是一個list

>>> def f(x):
	pass

>>> callable(fc)
Traceback (most recent call last):
  File "<pyshell#3>", line 1, in <module>
    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

字串函式

str.capitalize() 首字母大寫
str.replace('x','y',count) 字串替換 count 替換幾次
str.split(“”，sep) 將字串轉換為串列，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']
>>>

序列函式

filter() 過濾函式
filter(f,l) 將l串列中的值傳給函式f進行判斷，保留滿足要求的數值函式return True

zip() 將兩個串列的值進行對應，以元組存放在串列中，以最短的為組合數

map(None,a,b) 將串列a、b的值對應起來傳給None函式，None可以作為函式

fc(x,y)
reduce(fc,list) 將串列list的值依次傳輸給函式fc

>>> def f(x):
	if x>5:
		return True


>>> l = [1,2,3,5,6,2,3,6,7,8]
>>> filter(f,l)
<filter object at 0x00000220AC4C95E0>
>>> 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 "<pyshell#29>", line 1, in <module>
    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時需要匯入相應的模塊，

reduce用來計算階乘很方便，根據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

轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/153376.html

標籤：Python

上一篇：LeetCode 46. 全排列

下一篇：Python學習筆記：模塊學習