Python内置函数示例
abs()
返回数字绝对值
>>> abs(-100) 100 >>> abs(10) 10 >>>
all()
判断给定的可迭代参数 iterable 中的所有元素是否都为 TRUE,如果是返回 True,否则返回 False
>>> all([100,100,100]) True >>> all([3,0,1,1]) False >>>
any()
判断给定的可迭代参数 iterable 是否全部为 False,则返回 False,如果有一个为 True,则返回 True
>>> any([0,0,0,0]) False >>> any([0,0,0,1]) True >>>
ascii()
调用对象的repr()方法,获取该方法的返回值
>>> ascii(‘test‘) "‘test‘" >>>
bin()
将十进制转换为二进制
>>> bin(100) ‘0b1100100‘ >>>
oct()
将十进制转换为八进制
>>> oct(100) ‘0o144‘ >>>
hex()
将十进制转换为十六进制
>>> hex(100) ‘0x64‘ >>>
bool()
测试对象是True,还是False
>>> bool(1) True >>> bool(-1) True >>> bool() False >>>
bytes()
将一个字符转换为字节类型
>>> s = "blxt" >>> bytes(s,encoding=‘utf-8‘) b‘blxt‘ >>>
str()
将字符、数值类型转换为字符串类型
>>> str(123) ‘123‘ >>>
callable()
检查一个对象是否是可调用的
False >>> callable(str) True >>> callable(int) True >>> callable(0) False >>>
chr()
查看十进制整数对应的ASCll字符
>>> chr(100) ‘d‘ >>>
ord()
查看某个ascii对应的十进制
>>> ord(‘a‘) 97 >>>
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
#!/usr/bin/python # -*- coding: UTF-8 -*- class A(object): bar = 1 def func1(self): print (‘foo‘) @classmethod def func2(cls): print (‘func2‘) print (cls.bar) cls().func1() # 调用 foo 方法
输出结果:
func2 1 foo
compile()
将字符串编译成python能识别或者可以执行的代码。也可以将文字读成字符串再编译
>>> blxt = "print(‘hello‘)" >>> test = compile(blxt,‘‘,‘exec‘) >>> test <code object <module> at 0x02E9B840, file "", line 1> >>> exec(test) hello >>>
complex()
创建一个复数
>>> complex(13,18) (13+18j) >>>
delattr()
删除对象属性
#!/usr/bin/python # -*- coding: UTF-8 -*- class Coordinate: x = 10 y = -5 z = 0 point1 = Coordinate() print(‘x = ‘,point1.x) print(‘y = ‘,point1.y) print(‘z = ‘,point1.z) delattr(Coordinate, ‘z‘) print(‘--删除 z 属性后--‘) print(‘x = ‘,point1.x) print(‘y = ‘,point1.y) # 触发错误 print(‘z = ‘,point1.z)
输出结果:
>>> x = 10 y = -5 z = 0 --删除 z 属性后-- x = 10 y = -5 Traceback (most recent call last): File "C:\Users\fdgh\Desktop\test.py", line 22, in <module> print(‘z = ‘,point1.z) AttributeError: ‘Coordinate‘ object has no attribute ‘z‘ >>>
dict()
创建数据字典
>>> dict() {} >>> dict(a=1,b=2) {‘a‘: 1, ‘b‘: 2} >>>
dir()
函数不带参数时,返回当前范围内的变量、方法和定义的类型列表
>>> dir() [‘Coordinate‘, ‘__annotations__‘, ‘__builtins__‘, ‘__doc__‘, ‘__file__‘, ‘__loader__‘, ‘__name__‘, ‘__package__‘, ‘__spec__‘, ‘point1‘, ‘y‘] >>>
divmod()
分别取商和余数
>>> divmod(11,2) (5, 1) >>>
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
>>> blxt = [‘a‘,‘b‘,‘c‘,‘d‘] >>> list(enumerate(blxt)) [(0, ‘a‘), (1, ‘b‘), (2, ‘c‘), (3, ‘d‘)] >>>
eval()
将字符串str当成有效表达式来求值并返回计算结果取出字符串中内容
>>> blxt = "5+1+2" >>> eval(blxt) 8 >>>
exec()
执行字符串或complie方法编译过的字符串,没有返回值
>>> blxt = "print(‘hello‘)" >>> test = compile(blxt,‘‘,‘exec‘) >>> test <code object <module> at 0x02E9B840, file "", line 1> >>> exec(test) hello >>>
filter()
过滤器,构建一个序列
#过滤列表中所有奇数 #!/usr/bin/python # -*- coding: UTF-8 -*- def is_odd(n): return n % 2 == 1 newlist = filter(is_odd, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) print(newlist)
输出结果:
[ 1, 3, 5, 7, 9 ]
float()
将一个字符串或整数转换为浮点数
>>> float(3) 3.0 >>> float(10) 10.0 >>>
format()
格式化输出字符串
>>> "{0} {1} {3} {2}".format("a","b","c","d") ‘a b d c‘ >>> print("网站名:{name},地址:{url}".format(name="blxt",url="www.blxt.best")) 网站名:blxt,地址:www.blxt.best >>>
frozenset()
创建一个不可修改的集合
>>> frozenset([2,4,6,6,7,7,8,9,0]) frozenset({0, 2, 4, 6, 7, 8, 9}) >>>
getattr()
获取对象属性
>>>class A(object): ... bar = 1 ... >>> a = A() >>> getattr(a, ‘bar‘) # 获取属性 bar 值 1 >>> getattr(a, ‘bar2‘) # 属性 bar2 不存在,触发异常 Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: ‘A‘ object has no attribute ‘bar2‘ >>> getattr(a, ‘bar2‘, 3) # 属性 bar2 不存在,但设置了默认值 3 >>>
globals()
返回一个描述当前全局变量的字典
>>> print(globals()) # globals 函数返回一个全局变量的字典,包括所有导入的变量。 {‘__builtins__‘: <module ‘__builtin__‘ (built-in)>, ‘__name__‘: ‘__main__‘, ‘__doc__‘: None, ‘a‘: ‘runoob‘, ‘__package__‘: None}
hasattr()
函数用于判断对象是否包含对应的属性
>>>class A(object): ... bar = 1 ... >>> a = A() >>> hasattr(a,‘bar‘) True >>> hasattr(a,‘test‘) False
hash()
返回对象的哈希值
>>>class A(object): ... bar = 1 ... >>> a = A() >>> hash(a) -2143982521 >>>
help()
返回对象的帮助文档
>>>class A(object): ... bar = 1 ... >>> a = A() >>> help(a) Help on A in module __main__ object: class A(builtins.object) | Data descriptors defined here: | | __dict__ | dictionary for instance variables (if defined) | | __weakref__ | list of weak references to the object (if defined) | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | bar = 1 >>>
id()
返回对象的内存地址
>>>class A(object): ... bar = 1 ... >>> a = A() >>> id(a) 56018040 >>>
input()
获取用户输入内容
>>> input() ... test ‘test‘ >>>
int()
用于将一个字符串或数字转换为整型
>>> int(‘14‘,16) 20 >>> int(‘14‘,8) 12 >>> int(‘14‘,10) 14 >>>
isinstance()
来判断一个对象是否是一个已知的类型,类似 type()
>>> test = 100 >>> isinstance(test,int) True >>> isinstance(test,str) False >>>
issubclass()
用于判断参数 class 是否是类型参数 classinfo 的子类
#!/usr/bin/python # -*- coding: UTF-8 -*- class A: pass class B(A): pass print(issubclass(B,A)) # 返回 True
iter()
返回一个可迭代对象,sentinel可省略
>>>lst = [1, 2, 3] >>> for i in iter(lst): ... print(i) ... 1 2 3
len()
返回对象的长度
>>> dic = {‘a‘:100,‘b‘:200} >>> len(dic) 2 >>>
list()
返回可变序列类型
>>> a = (123,‘xyz‘,‘zara‘,‘abc‘) >>> list(a) [123, ‘xyz‘, ‘zara‘, ‘abc‘] >>>
map()
返回一个将function应用于iterable中每一项并输出其结果的迭代器
>>>def square(x) : # 计算平方数 ... return x ** 2 ... >>> map(square, [1,2,3,4,5]) # 计算列表各个元素的平方 [1, 4, 9, 16, 25] >>> map(lambda x: x ** 2, [1, 2, 3, 4, 5]) # 使用 lambda 匿名函数 [1, 4, 9, 16, 25] # 提供了两个列表,对相同位置的列表数据进行相加 >>> map(lambda x, y: x + y, [1, 3, 5, 7, 9], [2, 4, 6, 8, 10]) [3, 7, 11, 15, 19]
max()
返回最大值
>>> max (1,2,3,4,5,6,7,8,9) 9 >>>
min()
返回最小值
>>> min (1,2,3,4,5,6,7,8) 1 >>>
memoryview()
返回给定参数的内存查看对象(memory view)
>>>v = memoryview(bytearray("abcefg", ‘utf-8‘)) >>> print(v[1]) 98 >>> print(v[-1]) 103 >>> print(v[1:4]) <memory at 0x10f543a08> >>> print(v[1:4].tobytes()) b‘bce‘ >>>
next()
返回可迭代对象的下一个元素
>>> a = iter([1,2,3,4,5]) >>> next(a) 1 >>> next(a) 2 >>> next(a) 3 >>> next(a) 4 >>> next(a) 5 >>> next(a) Traceback (most recent call last): File "<pyshell#72>", line 1, in <module> next(a) StopIteration >>>
object()
返回一个没有特征的新对象
>>> a = object() >>> type(a) <class ‘object‘> >>>
open()
返回文件对象
>>>f = open(‘test.txt‘) >>> f.read() ‘123/123/123‘
pow()
base为底的exp次幂,如果mod给出,取余
>>> pow (3,1,4) 3 >>>
print()
打印对象
class property()
返回property属性
class C(object): 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 x = property(getx, setx, delx, "I‘m the ‘x‘ property.")
range()
生成一个不可变序列
>>> range(10) range(0, 10) >>>
reversed()
返回一个反向的iterator
>>> a = ‘test‘ >>> a ‘test‘ >>> print(list(reversed(a))) [‘t‘, ‘s‘, ‘e‘, ‘t‘] >>>
round()
四舍五入
>>> round (3.33333333,1) 3.3 >>>
class set()
返回一个set对象,可实现去重
>>> a = [1,2,3,4,5,5,6,5,4,3,2] >>> set(a) {1, 2, 3, 4, 5, 6} >>>
class slice()
返回一个表示有1range所指定的索引集的slice对象
>>> a = [1,2,3,4,5,5,6,5,4,3,2] >>> a[slice(0,3,1)] [1, 2, 3] >>>
sorted()
对所有可迭代的对象进行排序操作
>>> a = [1,2,3,4,5,5,6,5,4,3,2] >>> sorted(a,reverse=True) [6, 5, 5, 5, 4, 4, 3, 3, 2, 2, 1] >>>
@staticmethod
将方法转换为静态方法
#!/usr/bin/python # -*- coding: UTF-8 -*- class C(object): @staticmethod def f(): print(‘blxt‘); C.f(); # 静态方法无需实例化 cobj = C() cobj.f() # 也可以实例化后调用
输出结果:
test test
sum()
求和
a = [1,2,3,4,5,5,6,5,4,3,2] >>> sum(a) 40 >>>
super()
返回一个代理对象
class A: def add(self, x): y = x+1 print(y) class B(A): def add(self, x): super().add(x) b = B() b.add(2) # 3
tuple()
不可变的序列类型
>>> a = ‘www‘ >>> b =tuple(a) >>> b (‘w‘, ‘w‘, ‘w‘) >>>
zip()
将可迭代的对象作为参数,将对象中对应的元素打包成一个个元组,然后返回由这些元组组成的列表
>>>a = [1,2,3] >>> b = [4,5,6] >>> c = [4,5,6,7,8] >>> zipped = zip(a,b) # 打包为元组的列表 [(1, 4), (2, 5), (3, 6)] >>> zip(a,c) # 元素个数与最短的列表一致 [(1, 4), (2, 5), (3, 6)] >>> zip(*zipped) # 与 zip 相反,*zipped 可理解为解压,返回二维矩阵式 [(1, 2, 3), (4, 5, 6)]