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  • python内置函数的简单使用和介绍

    """
    内置函数的简单使用和介绍
    参考链接:https://docs.python.org/3/library/functions.html


    """
    1.
    abs() # 绝对值
    """
    n = abs(-10)
    print (n)
    # 10



    """
    2.
    all() # 全为真,输出Ture , 则输出Flase
    any() # 只要有真,输出Ture,则输出Flase

    0,None,"",[],(),{} # False
    """
    n1 = all([1,2,3,[],None])
    print (n1)
    # False
    n2 = any([1,0,"",[]])
    print (n2)
    # True
    

      


    """
    3.
    ascii()
    自动执行对象的__repr__方法
    """
    class Foo:
        def __repr__(self):
            return "444"
    n = ascii(Foo())
    print (n)
    # 444
    

      



    """
    4.
    bin() # 将十进制转为二进制 0b 表示二进制
    oct() # 将十进制转为八进制 0o 表示八进制
    hex() # 将十进制转为十六进制 0x 表示十六进制
    """
    print (bin(5))
    print (oct(9))
    print (hex(27))
    # 0b101
    # 0o11
    # 0x1b
    

      



    """
    5.
    bool() 布尔值
    0,None,"",[],(),{} 表示False
    """


    """
    6.
    bytes()
    utf8 编码,一个汉字3个字节
    gbk 编码,一个汉字2个字节
    一个字节 == 8位

    str()
    字节转化为字符串
    """
    # 将字符串转换为字节类型,系统中的表现形式为16进制
    # bytes(字符串,编码格式)
    s = "中国"
    n3 = bytes(s,encoding="utf-8")
    print (n3)
    # b'xe4xb8xadxe5x9bxbd'
    n4 = bytes(s,encoding="gbk")
    print (n4)
    # b'xd6xd0xb9xfa'
    
    n5 = str(b'xd6xd0xb9xfa',encoding="gbk")
    print (n5)
    # 中国
    n6 = str(b'xe4xb8xadxe5x9bxbd',encoding="utf-8")
    print (n6)
    # 中国
    

      




    """
    7.
    callable()
    检测传递的值是否可以调用
    """
    def f1():
        pass
    f1()
    f2 = 123
    print (callable(f1))
    # True
    print (callable(f2))
    # False
    

      



    """
    8.
    chr()
    ord()
    输出 ASCII的对应关系,chr()输出十进制位置的字符,ord()输出字符在ASCii表的位置
    """
    print (chr(65))
    # A
    print (ord("A"))
    # 65
    
    # 实例1:生成6位数随机密码,纯字母
    # import random
    # li = []
    # for i in range(6):
    #     temp = chr(random.randrange(65,91))
    #     li.append(temp)
    # print (li)
    # result = "".join(li)
    # print (result)
    
    # 实例2:生成8位数随机密码,带数字,字母
    import random
    li = []
    for i in range(8):
        r = random.randrange(0,6)   # 让生成数字的位置随机
        if r == 2 or r == 5:
            num = random.randrange(0,10)
            li.append(str(num))
        else:
            temp = random.randrange(65,91)
            c = chr(temp)
            li.append(c)
    result = "".join(li)
    print (result)
    # 3E4JVHF8
    

      



    """
    9.
    compile() # 编译,将字符串编译成python代码
    eval() # 执行表达式,并且获取结果
    exec() # 执行python代码

    注:eval有返回值,exec没返回值
    python hello.py 过程:
    1.读取文件内容open,str 到内存
    2.python,把字符串 -> 编译 -> 特殊代码
    3.执行代码
    """
    s = "print('hello,python~')"
    r = compile(s,"<string>","exec")
    exec (r)
    # hello,python~
    ss = "8*8+5"
    print (eval(ss))
    # 69
    

      


    """
    10.
    dir()
    help()
    快速获取模块,对象提供的功能
    """
    print (dir(tuple))
    print (help(tuple))
    

      




    """
    11.
    divmod()
    得到商和余数
    """
    n1,n2 = divmod(96,10)
    print (n1,n2)
    # 9 6
    


    """
    12.
    isinstance()
    用于判断,对象是否是某个类的实例
    """
    s1 = "hello"
    r = isinstance(s1,str)
    print (r)
    # True
    r1 = isinstance(s1,list)
    print (r1)
    # Flase
    

      


    """
    13.
    filter() # 函数返回值为Ture,将元素添加结果中
    # filter 循环第二个参数,让每个循环元素执行函数,如果函数返回值为Ture,表示函数合法
    map() # 将函数返回值添加结果中
    # (函数,可迭代的对象(可以for循环))
    """
    # 示例1
    def f1(args):
        result = []
        for item in args:
            if item > 22:
                result.append(item)
        return result
    li = [11,22,33,44,55,66,77,88]
    ret = f1(li)
    print (ret)
    # [33, 44, 55, 66, 77, 88]
    
    # 优化示例1
    def f2(a):
        if a > 22:
            return True
    ls1 = [11,22,33,44,55,66,77]
    res1 = filter(f2,ls1)
    print(list(res1))
    # [33, 44, 55, 66, 77]
    
    # 知识扩展,lambda 函数
    res2 = filter(lambda x:x > 22,ls1)
    print (res2) # 返回一个filter object
    # <filter object at 0x000000E275771748>
    print (list(res2))
    # [33, 44, 55, 66, 77]
    
    # 示例2
    def f1(args):
        result = []
        for i in args:
            result.append(i + 100)
        return result
    lst1 = [11,22,33,44,55,66]
    rest = f1(lst1)
    print (list(rest))
    # [111, 122, 133, 144, 155, 166]
    
    # 优化示例2,,,map函数
    def f2(a):
        return a + 100
    lst2 = [11,22,33,44,55,66]
    result1 = map(f2,lst2)
    print (list(result1))
    # [111, 122, 133, 144, 155, 166]
    
    # 优化示例2,map函数+lambda函数
    lst3 = [11,22,33,44,55,66]
    result2 = map(lambda a:a+100,lst3)
    print (list(result2))
    # [111, 122, 133, 144, 155, 166]



    """
    14.
    globals() # 所有的全局变量
    locals() # 所有的局部变量
    """
    name = "python"
    def show():
        a = 123
        b = 456
        print (locals())
        print (globals())
    show()
    # {'a': 123, 'b': 456}
    # {'result': '3VZ8B1V0', 'res1': <filter object at 0x000000ECFE24B5C0>, 'lst3': [11, 22, 33, 44, 55, 66], '__package__': None, 'f2': <function f2 at 0x000000ECFFCB9268>, 'ss': '8*8+5', 'n2': 6, 'n3': b'xe4xb8xadxe5x9bxbd', 'temp': 86, 's1': 'hello', 'n': '444', 'name': 'python', 'i': 7, 'rest': [111, 122, 133, 144, 155, 166], '__spec__': None, 'lst1': [11, 22, 33, 44, 55, 66], 'r1': False, 'num': 0, '__builtins__': <module 'builtins' (built-in)>, 'n6': '中国', 'random': <module 'random' from 'C:\Users\xieshengsen\AppData\Local\Programs\Python\Python35\lib\random.py'>, 's': "print('hello,python~')", '__file__': 'D:/PycharmProjects/高级自动化/模块学习/内置函数_v1.py', 'f1': <function f1 at 0x000000ECFFCBF510>, 'result2': <map object at 0x000000ECFE25EC88>, 'show': <function show at 0x000000ECFFCBF2F0>, 'ret': [33, 44, 55, 66, 77, 88], '__cached__': None, 'li': [11, 22, 33, 44, 55, 66, 77, 88], '__doc__': '
    内置函数的简单使用和介绍
    参考链接:https://docs.python.org/3/library/functions.html
    ', 'c': 'V', 'result1': <map object at 0x000000ECFE260D30>, 'Foo': <class '__main__.Foo'>, 'n1': 9, 'n5': '中国', 'r': True, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000000ECFDFEA898>, 'ls1': [11, 22, 33, 44, 55, 66, 77], 'lst2': [11, 22, 33, 44, 55, 66], 'res2': <filter object at 0x000000ECFE24B4A8>, 'n4': b'xd6xd0xb9xfa', '__name__': '__main__'}


    """
    15.
    hash()
    生成一个hash值(字符串)
    """
    has = "python"
    print (hash(has))
    # 839578881833832098
    

      



    """
    16.
    len()
    输出对象的长度
    """
    print(len("python"))
    # 6
    print (len("长城")) # python3,  python2 输出长度为6 (python3按字符,python2按字节)
    # 2
    

      



    """
    17.
    max() # 最大值
    min() # 最小值
    sun() # 求和
    """
    lit = [11,22,33,44,55]
    print (max(lit))
    print (min(lit))
    print (sum(lit))
    # 55
    # 11
    # 165
    

      



    """
    18.
    pow()
    求指数
    """
    print(pow(2,10))
    # 1024
    

      



    """
    19.
    reverse()
    反转
    """
    lit1 = [11,22,33,44,55,66]
    print (list(reversed(lit1)))
    # [66, 55, 44, 33, 22, 11]
    

      



    """
    20.
    round()
    四舍五入求值
    """
    print (round(1.4))
    print (round(1.8))
    # 1
    # 2
    

      



    """
    21.
    sorted()
    排序 等同于列表的sort
    """
    lit2 = [12,32,1,3,4,34,11,5]
    print (list(sorted(lit2)))
    # [1, 3, 4, 5, 11, 12, 32, 34]
    lit2.sort()
    print (lit2)
    # [1, 3, 4, 5, 11, 12, 32, 34]



    """
    22.
    zip()
    """
    l1 = ["hello",11,22,33]
    l2 = ["world",44,55,66]
    l3 = ["python",77,88,99]
    l4 = zip(l1,l2,l3)
    # print (list(l4))
    # # [('hello', 'world', 'python'), (11, 44, 77), (22, 55, 88), (33, 66, 99)]
    temp1 = list(l4)[0]
    print (temp1[0])
    ret1 = " ".join(temp1)
    print (ret1)
    # hello world python
    

      

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  • 原文地址:https://www.cnblogs.com/xieshengsen/p/7289963.html
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