当前位置 : 主页 > 编程语言 > python >

python常用内建函数

来源:互联网 收集:自由互联 发布时间:2021-06-25
1.map函数(对指定序列映射到指定函数,返回结果集) a=[1,3,5] b=[2,4,6] def mf(x,y): ... return x*y ... map(None,a,b) [(1, 2), (3, 4), (5, 6)] map(mf,a,b) [2, 12, 30] list(map(lambda x,y:x+y,[1,2,3],[4,5,6])) [5, 7, 9] 2

1.map函数(对指定序列映射到指定函数,返回结果集)

>>> a=[1,3,5]
>>> b=[2,4,6]
>>> def mf(x,y):
... return x*y
...
>>> map(None,a,b)
[(1, 2), (3, 4), (5, 6)]
>>> map(mf,a,b)
[2, 12, 30]

>>> list(map(lambda x,y:x+y,[1,2,3],[4,5,6]))
[5, 7, 9]

 

2.filter函数(对指定序列按照规则执行过滤操作,返回传入的参数)

>>> list(filter(lambda x:x%2,[1,2,3,4]))
[1, 3]
>>> list(filter(lambda x:x/2,[1,2,3,4]))
[2, 3, 4]

>>> filter(None,‘hello‘)
‘hello‘

3.reduce函数(对参数序列中元素进行累积)

>>> reduce(lambda x,y:x+y,[1,2,3,4,5],6)
21
>>> reduce(lambda x,y:x*y,[1,2,3,4,5],6)
720

>>> def f(x,y):
... return x*y
...
>>> l=range(1,6)
>>> reduce(f,l)
120

4.zip函数(将可迭代对象元素对应下标两两组合打包成包含元组的列表)

>>> a=[1,2,3]
>>> b=[4,5,6,7]
>>> print(list(zip(a,b)))
[(1, 4), (2, 5), (3, 6)]

5.setattr()、getattr()函数(分别为设置和获取对象的属性,对象的方法也是对象的属性)

>>> class A(object):
... name="milo"
... def click(self):
... print(123)
...
>>> a=A()
>>> x=getattr(a,"name")
>>> print x
milo
>>> y=getattr(a,"click")
>>> print y
<bound method A.click of <__main__.A object at 0x0000000003863358>>
>>> setattr(a,"age",18)
>>> m=getattr(a,"age")
>>> print(m)
18

6.callable(object)(如果参数可调用,返回true,否则返回false,类若有一个__call__()方法,实例可被调用)

>>> a=1
>>> callable(a)
False

>>> def func():
... pass
...
>>> callable(func)
True
>>> class A:
... def __call__(self,*args,**kwards):
... pass
...
>>> a=A()
>>> callable(a) s):
True

7.divmod(a,b)(返回商和余数组成的一对数字)

>>> divmod(5,2)
(2, 1)

8.isinstance(obj,classinfo)(如果参数是classinfo的实例,返回true,否则返回false)

>>> isinstance("abc",(int,str))
True
>>> isinstance(max,(int,str))
False
9.pow(x,y[,z])(返回x的y次方再除以z的余数)

>>> pow(3,2)
9
>>> pow(3,2,4)
1

10.字符串函数

(1)str.capitalize()(第一个字符串大写)

>>> st="i am a student"
>>> st.capitalize()
‘I am a student‘

(2)str.replace(obj1,obj2,num=str.count(obj1))(替换obj1为obj2)

>>> t=‘tast‘
>>> t.replace(‘a‘,‘e‘)
‘test‘
>>> t=‘taast‘
>>> t.replace(‘a‘,‘o‘,1)
‘toast‘

(3)str.split(obj,num)(以obj为分隔符切片str,指定分割num个obj)

>>> t=‘abcde‘
>>> t.split(‘c‘)
[‘ab‘, ‘de‘]
>>> t=‘abcdbcbce‘
>>> t.split(‘c‘,2)
[‘ab‘, ‘db‘, ‘bce‘]

(4)str.find(obj,beg=0,end=len(str))(如果obj在字符串中,返回索引值,不在,返回-1)

>>> st
‘i am a student‘
>>> st.find(‘student‘)
7
>>> st.index(‘am‘)
2
>>> st.find(‘studentsa‘)
-1

网友评论