盘点Python 63个内置函数
Posted cassielcode
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了盘点Python 63个内置函数相关的知识,希望对你有一定的参考价值。
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, I 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
以上是关于盘点Python 63个内置函数的主要内容,如果未能解决你的问题,请参考以下文章