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盘点Python 63个内置函数

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标签:UNC   iter   文件   bool   abs   filter   traceback   sort   python   

Python 内置函数最全汇总:
1 abs()
绝对值或复数的模

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

 

2 all()  
接受一个迭代器,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()  
接受一个迭代器,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() 方法,获得该方法的返回值

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 bin()
将十进制转换为二进制

In [35]: bin(10)
Out[35]: \0b1010\‘

 

6 oct()
将十进制转换为八进制

In [36]: oct(9)
Out[36]: \0o11\‘

 

7 hex()
将十进制转换为十六进制

In [37]: hex(15)
Out[37]: \0xf\‘

 

8 bool()  
测试一个对象是True, 还是False.

In [38]: bool([0,0,0])
Out[38]: True

In [39]: bool([])
Out[39]: False

In [40]: bool([1,0,1])
Out[40]: True

 

9 bytes()  
将一个字符串转换成字节类型

In [44]: s = "apple"

In [45]: bytes(s,encoding=\utf-8\‘)
Out[45]: b\apple\‘

 

10 str()  
将字符类型、数值类型等转换为字符串类型

In [46]: integ = 100

In [47]: str(integ)
Out[47]: \100\‘

 

11 callable()  
判断对象是否可以被调用,能被调用的对象就是一个callable 对象,比如函数 str, int 等都是可被调用的,但是例子4 中xiaoming这个实例是不可被调用的:

In [48]: callable(str)
Out[48]: True

In [49]: callable(int)
Out[49]: True

In [50]: xiaoming
Out[50]: id = 001, name = xiaoming

In [51]: callable(xiaoming)
Out[51]: False

 

12 chr()
查看十进制整数对应的ASCII字符

In [54]: chr(65)
Out[54]: \A\‘

 

13 ord()
查看某个ascii对应的十进制数

In [60]: ord(\A\‘)
Out[60]: 65

 

14 classmethod()  
classmethod 修饰符对应的函数不需要实例化,不需要 self 参数,但第一个参数需要是表示自身类的 cls 参数,可以来调用类的属性,类的方法,实例化对象等。

In [66]: class Student():
...: def __init__(self,id,name):
...: self.id = id
...: self.name = name
...: def __repr__(self):
...: return \id = \‘+self.id +\‘, name = \‘+self.name
...: @classmethod
...: def f(cls):
...: print(cls)

 

15 complie()  
将字符串编译成python 能识别或可以执行的代码,也可以将文字读成字符串再编译。

In [74]: s = "print(\‘helloworld\‘)"

In [75]: r = compile(s,"<string>", "exec")

In [76]: r
Out[76]: <code object <module> at 0x0000000005DE75D0, file "<string>", line 1>

In [77]: exec(r)
helloworld

 

16 complex()
创建一个复数

In [81]: complex(1,2)
Out[81]: (1+2j)

 

17 delattr()  
删除对象的属性

In [87]: delattr(xiaoming,\id\‘)

In [88]: hasattr(xiaoming,\id\‘)
Out[88]: False

 

18 dict()  
创建数据字典

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}

 

19 dir()  
不带参数时返回当前范围内的变量,方法和定义的类型列表;带参数时返回参数的属性,方法列表。

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\‘]

 

20 divmod()  
分别取商和余数

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

 


21 enumerate()  
返回一个可以枚举的对象,该对象的next()方法将返回一个元组。

In [98]: s = ["a","b","c"]
...: for i ,v in enumerate(s,1):
...: print(i,v)
...:
1 a
2 b
3 c

 


22 eval()  
将字符串str 当成有效的表达式来求值并返回计算结果取出字符串中内容

In [99]: s = "1 + 3 +5"
...: eval(s)
...:
Out[99]: 9

 


23 exec()  
执行字符串或complie方法编译过的字符串,没有返回值

In [74]: s = "print(\‘helloworld\‘)"

In [75]: r = compile(s,"<string>", "exec")

In [76]: r
Out[76]: <code object <module> at 0x0000000005DE75D0, file "<string>", line 1>

In [77]: exec(r)
helloworld

 

24 filter()  
过滤器,构造一个序列,等价于

[item for item in iterables if function(item)]
在函数中设定过滤条件,逐一循环迭代器中的元素,将返回值为True时的元素留下,形成一个filter类型数据。

In [101]: fil = filter(lambda x: x>10,[1,11,2,45,7,6,13])

In [102]: list(fil)
Out[102]: [11, 45, 13]

 

25 float()  
将一个字符串或整数转换为浮点数

In [103]: float(3)
Out[103]: 3.0

 


26 format()  
格式化输出字符串,format(value, format_spec)实质上是调用了value的format(format_spec)方法。

In [104]: print("i am {0},age{1}".format("tom",18))
i am tom,age18

 


27 frozenset()  

创建一个不可修改的集合。
In [105]: frozenset([1,1,3,2,3])
Out[105]: frozenset({1, 2, 3})

 


28 getattr()  

获取对象的属性
In [106]: getattr(xiaoming,\name\‘)
Out[106]: \xiaoming\‘

 


29 globals()  
返回一个描述当前全局变量的字典


30 hasattr()

In [110]: hasattr(xiaoming,\name\‘)
Out[110]: True

In [111]: hasattr(xiaoming,\id\‘)
Out[111]: False

 

31 hash()  
返回对象的哈希值

In [112]: hash(xiaoming)
Out[112]: 6139638

 


32 help()  
返回对象的帮助文档

In [113]: help(xiaoming)
Help on Student in module __main__ object:

class Student(builtins.object)
| Methods defined here:
|
| __init__(self, id, name)
|
| __repr__(self)
|
| ----------------------------------------------------------------------
| Data descriptors defined here:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)

 

33 id()  
返回对象的内存地址

In [115]: id(xiaoming)
Out[115]: 98234208

 


34 input()  
获取用户输入内容

In [116]: input()
aa
Out[116]: \aa\‘

 


35 int()  

int(x, base =10) , x可能为字符串或数值,将x 转换为一个普通整数。如果参数是字符串,那么它可能包含符号和小数点。如果超出了普通整数的表示范围,一个长整数被返回。
In [120]: int(\12\‘,16)
Out[120]: 18

 


36 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

 

37 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

 

38 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 理解为迭代对象的哨兵,一旦迭代到此元素,立即终止:

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__方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): #支持迭代协议(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

 

39 len(s)
返回对象的长度(元素个数)

In [83]: dic = {\a\‘:1,\‘b\‘:3}

In [84]: len(dic)
Out[84]: 2

 

40 list([iterable])
返回可变序列类型

In [85]: list(map(lambda x: x%2==1, [1,3,2,4,1]))
Out[85]: [True, True, False, False, True]

 


41 map(function, iterable, …)
返回一个将 function 应用于 iterable 中每一项并输出其结果的迭代器:

In [85]: list(map(lambda x: x%2==1, [1,3,2,4,1]))
Out[85]: [True, True, False, False, True]
可以传入多个iterable对象,输出长度等于最短序列的长度:
In [88]: list(map(lambda x,y: x%2==1 and y%2==0, [1,3,2,4,1],[3,2,1,2]))
Out[88]: [False, True, False, False]


42 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\‘}

 

43 min(iterable,*[, key, default])
返回最小值


44 memoryview(obj)
返回由给定实参创建的“内存视图”对象, Python 代码访问一个对象的内部数据,只要该对象支持 缓冲区协议 而无需进行拷贝


45 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:

 

46 object()
返回一个没有特征的新对象。object 是所有类的基类。

In [137]: o = object()

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

 

47 open(file)
返回文件对象

In [146]: fo = open(\D:/a.txt\‘,mode=\‘r\‘, encoding=\‘utf-8\‘)

In [147]: fo.read()
Out[147]: \\ufefflife is not so long,\nI use Python to play.\‘

mode取值表:字符意义

\‘r\‘  读取(默认)
\‘w\‘  写入,并先截断文件
\‘x\‘ 排它性创建,如果文件已存在则失败
\‘a\‘ 写入,如果文件存在则在末尾追加
\‘b\‘ 二进制模式
\‘t\‘ 文本模式(默认)
\‘+\‘ 打开用于更新(读取与写入)

 

48 pow(base, exp[, mod])
base为底的exp次幂,如果mod给出,取余

In [149]: pow(3, 2, 4)
Out[149]: 1

 


49 print(objects)
打印对象,此函数不解释


50 class property(fget=None, fset=None, fdel=None, doc=None)
返回 property 属性,典型的用法:

class C:
def __init__(self):
self._x = None

def getx(self):
return self._x

def setx(self, value):
self._x = value

def delx(self):
del self._x
# 使用property类创建 property 属性
x = property(getx, setx, delx, "I\‘m the \‘x\‘ property.")
使用python装饰器,实现与上完全一样的效果代码:
class C:
def __init__(self):
self._x = None

@property
def x(self):
return self._x

@x.setter
def x(self, value):
self._x = value

@x.deleter
def x(self):
del self._x

 

51 range(stop)
range(start, stop[,step])
生成一个不可变序列:

In [153]: range(11)
Out[153]: range(0, 11)

In [154]: range(0,11,1)
Out[154]: range(0, 11)

 

52 reversed(seq)
返回一个反向的 iterator:

In [155]: rev = reversed([1,4,2,3,1])

In [156]: for i in rev:
...: print(i)
...:
1
3
2
4
1

 

53 round(number[, ndigits])
四舍五入,ndigits代表小数点后保留几位:

In [157]: round(10.0222222, 3)
Out[157]: 10.022

 


54 class set([iterable])
返回一个set对象,可实现去重:

In [159]: a = [1,4,2,3,1]

In [160]: set(a)
Out[160]: {1, 2, 3, 4}

 

55 class slice(stop)

class slice(start, stop[, step])
返回一个表示由 range(start, stop, step) 所指定索引集的 slice对象

In [170]: a = [1,4,2,3,1]

In [171]: a[slice(0,5,2)] #等价于a[0:5:2]
Out[171]: [1, 2, 1]

 

56 sorted(iterable, *, key=None, reverse=False)

排序:

In [174]: a = [1,4,2,3,1]

In [175]: sorted(a,reverse=True)
Out[175]: [4, 3, 2, 1, 1]

In [178]: a = [{\name\‘:\‘xiaoming\‘,\‘age\‘:18,\‘gender\‘:\‘male\‘},{\‘name\‘:\‘
...: xiaohong\,\‘age\‘:20,\‘gender\‘:\‘female\‘}]
In [180]: sorted(a,key=lambda x: x[\age\‘],reverse=False)
Out[180]:
[{\name\‘: \‘xiaoming\‘, \‘age\‘: 18, \‘gender\‘: \‘male\‘},
{\name\‘: \‘xiaohong\‘, \‘age\‘: 20, \‘gender\‘: \‘female\‘}]

 

57 @staticmethod
将方法转换为静态方法,不做解释


58 class str(object=\‘\‘)
返回一个 str版本的 object,str 是内置字符串 class


59 sum(iterable, /, start=0)
求和:

In [181]: a = [1,4,2,3,1]

In [182]: sum(a)
Out[182]: 11

In [185]: sum(a,10) #求和的初始值为10
Out[185]: 21

 

60 super([type[, object-or-type]])
返回一个代理对象,它会将方法调用委托给 type 的父类或兄弟类


61 tuple([iterable])
虽然被称为函数,但 tuple 实际上是一个不可变的序列类型


62 class type(object)

class type(name, bases, dict)

传入一个参数时,返回 object 的类型:

In [186]: type(xiaoming)
Out[186]: __main__.Student

In [187]: type(tuple())
Out[187]: tuple

 

63 zip(*iterables)
创建一个聚合了来自每个可迭代对象中的元素的迭代器:

In [188]: x = [3,2,1]
In [189]: y = [4,5,6]
In [190]: list(zip(y,x))
Out[190]: [(4, 3), (5, 2), (6, 1)]


In [191]: a = range(5)
In [192]: b = list(\abcde\‘)
In [193]: b
Out[193]: [\a\‘, \‘b\‘, \‘c\‘, \‘d\‘, \‘e\‘]
In [194]: [str(y) + str(x) for x,y in zip(a,b)]
Out[194]: [\a0\‘, \‘b1\‘, \‘c2\‘, \‘d3\‘, \‘e4\‘]

14:16:21

盘点Python 63个内置函数

标签:UNC   iter   文件   bool   abs   filter   traceback   sort   python   

原文地址:https://www.cnblogs.com/cassielcode/p/12468863.html

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