关于python:福利来了Python内置函数最全总结

1 abs()

绝对值或复数的模

In [1]: abs(-6)
Out[1]: 6

2 all()

承受一个迭代器，如果迭代器的所有元素都为真，那么返回 True，否则返回 False

In [2]: all([1,0,3,6])
Out[2]: False
 
In [3]: all([1,2,3])
Out[3]: True

3 any()

承受一个迭代器，如果迭代器里有一个元素为真，那么返回 True，否则返回 False

In [4]: any([0,0,0,[]])
Out[4]: False
 
In [5]: any([0,0,1])
Out[5]: True

4 ascii()

调用对象的 repr() 办法，取得该办法的返回值
In [30]: class Student():
    ...:     def __init__(self,id,name):
    ...:         self.id = id
    ...:         self.name = name
    ...:     def __repr__(self):
    ...:         return 'id ='+self.id +', name ='+self.name
 
In [33]: print(xiaoming)
id = 001, name = xiaoming
 
In [34]: ascii(xiaoming)
Out[34]: 'id = 001, name = xiaoming'

5 dict()

创立数据字典

In [92]: dict()
Out[92]: {}
 
In [93]: dict(a='a',b='b')
Out[93]: {'a': 'a', 'b': 'b'}
 
In [94]: dict(zip(['a','b'],[1,2]))
Out[94]: {'a': 1, 'b': 2}
 
In [95]: dict([('a',1),('b',2)])
Out[95]: {'a': 1, 'b': 2}

6 dir()

不带参数时返回以后范畴内的变量，办法和定义的类型列表；带参数时返回参数的属性，办法列表。

In [96]: dir(xiaoming)
Out[96]:
['__class__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__',
 
 'name']

7 divmod()

别离取商和余数

In [97]: divmod(10,3)
Out[97]: (3, 1)

8  isinstance(object, classinfo)

判断 object 是否为类 classinfo 的实例，是返回 true

In [20]: class Student():
    ...:     ...:     def __init__(self,id,name):
    ...:     ...:         self.id = id
    ...:     ...:         self.name = name
    ...:     ...:     def __repr__(self):
    ...:     ...:         return 'id ='+self.id +', name ='+self.name
    ...:
 
In [21]: xiaoming = Student('001','xiaoming')
 
In [22]: isinstance(xiaoming,Student)
Out[22]: True

9 issubclass(class, classinfo)

如果 class 是 classinfo 类的子类，返回 True：

In [27]: class undergraduate(Student):
    ...:     def studyClass(self):
    ...:         pass
    ...:     def attendActivity(self):
    ...:         pass
    ...:
 
In [28]: issubclass(undergraduate,Student)
Out[28]: True
 
In [29]: issubclass(object,Student)
Out[29]: False
 
In [30]: issubclass(Student,object)
Out[30]: True
如果 class 是 classinfo 元组中某个元素的子类，也会返回 True
In [26]: issubclass(int,(int,float))
Out[26]: True

10 iter(object, sentinel)

返回一个可迭代对象, sentinel 可省略

In [72]: lst = [1,3,5]
 
In [73]: for i in iter(lst):
    ...:     print(i)
    ...:
1
3
5

sentinel 了解为迭代对象的哨兵，一旦迭代到此元素，立刻终止：

In [81]: class TestIter(object):
    ...:         def __init__(self):
    ...:             self.l=[1,3,2,3,4,5]
    ...:             self.i=iter(self.l)
    ...:         def __call__(self):  #定义了__call__办法的类的实例是可调用的
    ...:             item = next(self.i)
    ...:             print ("__call__ is called,which would return",item)
    ...:             return item
    ...:         def __iter__(self): #反对迭代协定 (即定义有__iter__() 函数)
    ...:             print ("__iter__ is called!!")
    ...:             return iter(self.l)
    ...:
 
In [82]:     t = TestIter()
    ...:     t1 = iter(t, 3)
    ...:     for i in t1:
    ...:         print(i)
    ...:
__call__ is called,which would return 1
1
__call__ is called,which would return 3

11 max(iterable,*[, key, default])

返回最大值：

In [99]: max(3,1,4,2,1)
Out[99]: 4
 
In [100]: max((),default=0)
Out[100]: 0
 
In [89]: di = {'a':3,'b1':1,'c':4}
In [90]: max(di)
Out[90]: 'c'
 
In [102]: a = [{'name':'xiaoming','age':18,'gender':'male'},{'name':'...: xiaohong','age':20,'gender':'female'}]
In [104]: max(a,key=lambda x: x['age'])
Out[104]: {'name': 'xiaohong', 'age': 20, 'gender': 'female'}

12 min(iterable,*[, key, default])

返回最小值

13 memoryview(obj)

返回由给定实参创立的“内存视图”对象，Python 代码拜访一个对象的外部数据，只有该对象反对 缓冲区协定 而无需进行拷贝

14 next(iterator,[, default])

返回可迭代对象的下一个元素

In [129]: it = iter([5,3,4,1])
 
In [130]: next(it)
Out[130]: 5
 
In [131]: next(it)
Out[131]: 3
 
In [132]: next(it)
Out[132]: 4
 
In [133]: next(it)
Out[133]: 1
 
In [134]: next(it,0) #迭代到头，默认返回值为 0
Out[134]: 0
 
In [135]: next(it)
----------------------------------------------------------------------
StopIteration                        Traceback (most recent call last)
<ipython-input-135-bc1ab118995a> in <module>
----> 1 next(it)
 
StopIteration:

15 object()

返回一个没有特色的新对象。object 是所有类的基类。

In [137]: o = object()
 
In [138]: type(o)
Out[138]: object