python order函数_Python学习日记(十一) 内置函数

什么是内置函数?

就是Python中已经写好了的函数,可以直接使用

内置函数图表:

以3.6.2为例

内置函数分类:

一、反射相关

二、基础数据类型相关

1.和数字相关

(1)数据类型

a.bool()

把一个值转换成布尔值

li = ['',[],1,12,0]for i inli:print(bool(i))#False#False#True#True#False

b.int()

把一个值转换成整型

num = input('Please input a number:')print(10 +int(num))#Please input a number:20#30

c.float()

把一个整数或数字字符串转换成带小数点的数

print(float('123.5'),type(float('123.5'))) #123.5

print(float(-50.2),type(float(-50.2))) #-50.2

d.complex()

返回一个复数

a = 1 + 2jb= 2

print(complex(a)) #(1+2j)

print(complex(b)) #(2+0j)

print(complex(2,3)) #(2+3j)

(2)进制转换

a.bin()

将一个数以二进制字符串的方式表示

print(bin(2)) #0b10

print(bin(10)) #0b1010

b.oct()

把一个数转换成八进制的字符串

print(oct(20),type(oct(20))) #0o24

print(oct(8),type(oct(8))) #0o10

c.hex()

把一个数字转换成十六进制的字符串

print(hex(10),type(hex(10))) #0xa

print(hex(28),type(hex(28))) #0x1c

(3)数学运算

a.abs()

对一个数的值取绝对值,结果不改变原值

a = -5

print(abs(a)) #5

b.divmod()

返回一个以商和余数组成的元祖

print(divmod(10,5),type(divmod(10,5))) #(2, 0)

print(divmod(4,9)) #(0, 4)

c.round()

将浮点值四舍五入

importmath

Pi=math.piprint(round(Pi,4)) #3.1416

d.pow()

一般情况下给函数两个数可以计算次方,若给定三个数则在幂运算后再取余

print(pow(2,3)) #8

print(pow(2,0.5)) #1.4142135623730951

print(pow(3,2,2)) #1

e.sum()

print(sum([2,2,3,5,6,2,4])) #24

print(sum([2,2,3,5,6,2,4],10)) #34 这里只是先让10进行sum的运算

f.min()

print(min(-1,-2,2,3)) #-2

print(min(-1,-2,2,3,key=abs)) #-1

print(min('aab','aaab','bc',key=len)) #bc

g.max()

print(max(-4,-2,2,3)) #3

print(max(-4,-2,2,3,key=abs)) #-4

print(max('aab','aaab','bc',key=len)) #aaab

2.和数据结构相关

(1)序列

<1>列表和元祖

a.list()

将一个元祖或者字符串转化成一个列表

print(list('abcdefg')) #['a', 'b', 'c', 'd', 'e', 'f', 'g']

print(list((1,2,'l'))) #[1, 2, 'l']

b.tuple()

将一个列表转化为元祖

print(tuple([1,2,3,'h','k'])) #(1, 2, 3, 'h', 'k')

<2>相关内置函数

a.reversed()

函数返回一个反转的迭代器

l = [1,2,3,'h','k',True]

l2= reversed(l) #

print(l2) #不改变原列表并返回一个迭代器

for i inl2:print(i)#True#k#h#3#2#1

b.slice()

l = ['a',1,2,3,4,8,'h','k']

sli= slice(2,7,2) #切片顾头不顾尾

print(l[sli]) #[2, 4, 'h']

<3>字符串

a.str()

将对象转化为适合人阅读的格式

tu = (1,2,'h')

dic= {'k1' : 1,'k2' : 2}

li= [1,2,3,'h']

i= 123

print(str(tu),type(tu)) #(1, 2, 'h')

print(str(dic),type(dic)) #{'k1': 1, 'k2': 2}

print(str(li),type(li)) #[1, 2, 3, 'h']

print(str(i),type(i)) #123

b.format()

主要用于格式化输出也可以用于数学方面的研究

value = 'ox123'tu= ('value1','value2','value3')print('get value->{0}'.format(value)) #get value->ox123

print('{0} {1} {2}'.format(*tu)) #value1 value2 value3

'''数字格式化'''a= 12.579

print('{:.2f}'.format(a)) #12.58 保留小数点的后两位

print('{:+.2f}'.format(a)) #+12.58 带符号的保留小数点的后两位

print('{:-.2f}'.format(-a)) #-12.58 带符号的保留小数点的后两位

print('{:.0f}'.format(a)) #13 不带小数返回并对结果四舍五入

print('{:.2%}'.format(a/100)) #12.58% 结果以百分比格式输出

b= 1001

print('{:0>8d}'.format(b)) #00001001 数字补0(填充左边宽度为8)

print('{:*>8d}'.format(b)) #****1001 数字补*(填充左边宽度为8)

print('{:*<8d}'.format(b)) #1001**** 数字补*(填充右边宽度为8)

c= 10**10

print('{:,}'.format(c)) #10,000,000,000 结果以逗号的形式分隔

print('{:.2e}'.format(c)) #1.00e+10 结果以指数标准格式输出

d= 7

print('{:>5d}'.format(d)) #7 向右对齐

print('{:<5d}'.format(d)) #7 向左对齐

print('{:^5d}'.format(d)) #7 中间对齐

e= 15

print('{:b}'.format(e)) #1111 返回二进制

print('{:d}'.format(e)) #15 返回十进制

print('{:o}'.format(e)) #17 返回八进制

print('{:x}'.format(e)) #f 返回十六进制

print('{:#x}'.format(e)) #0xf 返回带格式输出的十六进制小写

print('{:#X}'.format(e)) #0XF 返回带格式输出的十六进制大写

c.bytes()

主要用在网络编程、照片和视频、爬取网页等二进制文件的时候

print(bytes('Python爬虫',encoding='utf-8')) #b'Pythonxe7x88xacxe8x99xab'

d.bytearray()

返回一个bytes数组

b = bytes('Python爬虫',encoding='utf-8') #b'Pythonxe7x88xacxe8x99xab'

print(bytearray(b)) #bytearray(b'Pythonxe7x88xacxe8x99xab')

e.memoryview()

在一个缓冲区中查看一个对象,返回值为一个元祖

v = memoryview(bytearray('abcdef','utf-8'))print(v[2]) #99

print(v[-1]) #102

print(v[1:5:2]) #

print(v[1:5:2].tobytes()) #b'bd'

f.ord()

以一个字符作为参数返回一个unicode值或者ascii值,返回值为一个对应的十进制整数

print(ord('a')) #97

print(ord('A')) #65

print(ord('az')) #TypeError 超过给定长度报错

g.chr()

以一个十进制或十六进制的整数作为参数,数字范围为0-1114111(16进制为0x10FFFF)，返回值为对应的ASCII字符

print(chr(65)) #A

print(chr(97)) #a

print(chr(0x35)) #5

h.ascii()

返回一个ascii字符,如果找不到这个ascii字符则通过repr()使用x,u或U编码的字符

print(ascii(10)) #10

print(ascii('a')) #'a'

print(ascii('中')) #'u4e2d'

i.repr()

将对象转化为供解释器读取的形式,返回一个string的格式

name = 'jane'

print('hello %r'%name) #hello 'jane'

print(repr('1')) #'1'

print(repr(1)) #1

(2)数据集合

<1>字典

a.dict()

<1>集合

a.set()

b.frozenset()

(3)相关内置函数

a.len()

b.enumerate()

c.all()

d.any()

e.zip()

f.filter()

g.map()

h.sorted()

三、作用域相关

1.locals()

找到当前作用域下所有的变量对应关系,并以字典返回

2.globals()

找到全局作用域下所有的变量对应关系,并以字典返回

a = 1b= 'hello'

deffunc():

c= 3

print(locals()) #{'c': 3}

print(globals()) #{'__name__': '__main__', '__loader__': <_frozen_importlib_external.sourcefileloader object at>,

#'func': , '__file__': 'C:/Users/Administrator/PycharmProjects/PYL/生成器/1.py',

#'__spec__': None, '__cached__': None, 'a': 1, '__builtins__': , 'b': 'hello',

#'__doc__': None, '__package__': None}

func()

四、面向对象相关

五、迭代器/生成器相关

1.range()

用于创建一个整数列表,常用在for循环中

li = list(range(0,11,2))print(li) #[0, 2, 4, 6, 8, 10]

2.__next__()

一个next对应一个值返回,如果这个迭代器已经没有值可以返回了那么就将报错

li = ['a',1,2]

iterator= li.__iter__()print(iterator.__next__()) #a

print(iterator.__next__()) #1

3.__iter__()

当一个具有可迭代数据使用__iter__()它会返回一个迭代器的内存地址

li = ['a',1,2]

iterator= li.__iter__()print(iterator) #

六、其他

1.输入输出

(1)input()

content = input('请输入一个数:')print(content)#请输入一个数:5#5

(2)print()

特殊字符分隔

print('a','b','c',sep = '&&',end = '') #a&&b&&c

将用户输入的数据直接写入文件

f = open('file',mode='w',encoding='utf-8')

content=input()print(content,sep=',',end='',file = f,flush=True) #file默认是输出到屏幕,如果设置文件句柄则输出到文件

#flush立即将内容输出到文件流,不留缓存

f.close()

2.内存相关

(1)hsah()

这里hash()中用到的参数必须是不可变数据类型,hash()完后结果会返回一串数字

print(hash(133)) #133

print(hash('aaaaa')) #-868214941

print(hash('aaaax')) #519685031

print(hash((1,2,3))) #-378539185

最直接的例子就是字典键的值,字典中的key是唯一的并且只能对应一个hash值

(2)id()

返回一个变量的内存地址

a = 5b= 'hello'c= [1,2]print(id(a)) #490310160

print(id(b)) #4872512

print(id(c)) #6656288

3.字符串类型代码的执行

(1)eval()

可以执行字符串类型的代码,有返回值,适用于简单计算

建议一般情况下不要使用eval()除非自己很明确要执行什么

print(eval('123')) #123

print(eval('1 + 2 + 3 + 4')) #10

(2)exec()

可以执行字符串类型的代码,无返回值,适用于简单流程控制

print(exec('123')) #None

print(exec('1 + 2 + 3 + 4 + 5')) #None

code = '''for i in [1,5,10]:

print(i*2)'''

exec(code)#2#10#20

(3)complie()

compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)

source:字符串或者AST

filename:代码文件的名称,如果不是从文件中读取代码则传递一些可辨认的值。当传入source参数时,filename参数传空即可

model:编译代码的种类 eval属于计算类、exec属于流程类、single属于交互类

计算类:

code = '2*5/10 + 6'ret= compile(code,'','eval')print(eval(ret)) #7.0

流程类:

code = '''print([i*i for i in range(10) if i > 5])'''ret= compile(code,'','exec')exec(ret) #[36, 49, 64, 81]

交互类:

code = "name = input('Please input your name:')"ret= compile(code,'','single')exec(ret)print(name)

4.文件操作相关

(1)open()

打开一个文件的相关操作

5.模块相关

(1)__import__()

#import time

time = __import__('time')print(time.time())

6.帮助

(1)help()

能够查看一个变量或类型的方法

help(bool)#Help on class bool in module builtins:# #class bool(int)#| bool(x) -> bool#|#| Returns True when the argument x is true, False otherwise.#| The builtins True and False are the only two instances of the class bool.#| The class bool is a subclass of the class int, and cannot be subclassed.#|#| Method resolution order:#| bool#| int#| object#|#| Methods defined here:#|#| __and__(self, value, /)#| Return self&value.#|#| __new__(*args, **kwargs) from builtins.type#| Create and return a new object. See help(type) for accurate signature.#|#| __or__(self, value, /)#| Return self|value.#|#| __rand__(self, value, /)#| Return value&self.#|#| __repr__(self, /)#| Return repr(self).#|#| __ror__(self, value, /)#| Return value|self.#|#| __rxor__(self, value, /)#| Return value^self.#|#| __str__(self, /)#| Return str(self).#|#| __xor__(self, value, /)#| Return self^value.#|#| ----------------------------------------------------------------------#| Methods inherited from int:#|#| __abs__(self, /)#| abs(self)#|#| __add__(self, value, /)#| Return self+value.#|#| __bool__(self, /)#| self != 0#|#| __ceil__(...)#| Ceiling of an Integral returns itself.#|#| __divmod__(self, value, /)#| Return divmod(self, value).#|#| __eq__(self, value, /)#| Return self==value.#|#| __float__(self, /)#| float(self)#|#| __floor__(...)#| Flooring an Integral returns itself.#|#| __floordiv__(self, value, /)#| Return self//value.#|#| __format__(...)#| default object formatter#|#| __ge__(self, value, /)#| Return self>=value.#|#| __getattribute__(self, name, /)#| Return getattr(self, name).#|#| __getnewargs__(...)#|#| __gt__(self, value, /)#| Return self>value.#|#| __hash__(self, /)#| Return hash(self).#|#| __index__(self, /)#| Return self converted to an integer, if self is suitable for use as an index into a list.#|#| __int__(self, /)#| int(self)#|#| __invert__(self, /)#| ~self#|#| __le__(self, value, /)#| Return self<=value.#|#| __lshift__(self, value, /)#| Return self<>self.#|#| __rshift__(self, value, /)#| Return self>>value.#|#| __rsub__(self, value, /)#| Return value-self.#|#| __rtruediv__(self, value, /)#| Return value/self.#|#| __sizeof__(...)#| Returns size in memory, in bytes#|#| __sub__(self, value, /)#| Return self-value.#|#| __truediv__(self, value, /)#| Return self/value.#|#| __trunc__(...)#| Truncating an Integral returns itself.#|#| bit_length(...)#| int.bit_length() -> int#|#| Number of bits necessary to represent self in binary.#| >>> bin(37)#| '0b100101'#| >>> (37).bit_length()#| 6#|#| conjugate(...)#| Returns self, the complex conjugate of any int.#|#| from_bytes(...) from builtins.type#| int.from_bytes(bytes, byteorder, *, signed=False) -> int#|#| Return the integer represented by the given array of bytes.#|#| The bytes argument must be a bytes-like object (e.g. bytes or bytearray).#|#| The byteorder argument determines the byte order used to represent the#| integer. If byteorder is 'big', the most significant byte is at the#| beginning of the byte array. If byteorder is 'little', the most#| significant byte is at the end of the byte array. To request the native#| byte order of the host system, use `sys.byteorder' as the byte order value.#|#| The signed keyword-only argument indicates whether two's complement is#| used to represent the integer.#|#| to_bytes(...)#| int.to_bytes(length, byteorder, *, signed=False) -> bytes#|#| Return an array of bytes representing an integer.#|#| The integer is represented using length bytes. An OverflowError is#| raised if the integer is not representable with the given number of#| bytes.#|#| The byteorder argument determines the byte order used to represent the#| integer. If byteorder is 'big', the most significant byte is at the#| beginning of the byte array. If byteorder is 'little', the most#| significant byte is at the end of the byte array. To request the native#| byte order of the host system, use `sys.byteorder' as the byte order value.#|#| The signed keyword-only argument determines whether two's complement is#| used to represent the integer. If signed is False and a negative integer#| is given, an OverflowError is raised.#|#| ----------------------------------------------------------------------#| Data descriptors inherited from int:#|#| denominator#| the denominator of a rational number in lowest terms#|#| imag#| the imaginary part of a complex number#|#| numerator#| the numerator of a rational number in lowest terms#|#| real#| the real part of a complex number

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7.调用相关

(1)callable()

判断参数是否是一个可调用的函数名,若是则True,不是则False

a = 1

print(callable(a)) #False

deffunc():return 5

print(callable(func)) #True

print(callable(func())) #False

8.查看内置属性

(1)dir()

查看一个参数或变量的属性

print(dir([])) #['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

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