python内置函数的简单使用和介绍

Posted 2020-10-01

"""
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‘\\xe4\\xb8\\xad\\xe5\\x9b\\xbd‘
n4 = bytes(s,encoding="gbk")
print (n4)
# b‘\\xd6\\xd0\\xb9\\xfa‘

n5 = str(b‘\\xd6\\xd0\\xb9\\xfa‘,encoding="gbk")
print (n5)
# 中国
n6 = str(b‘\\xe4\\xb8\\xad\\xe5\\x9b\\xbd‘,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‘\\xe4\\xb8\\xad\\xe5\\x9b\\xbd‘, ‘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__‘: ‘\\n内置函数的简单使用和介绍\\n参考链接：https://docs.python.org/3/library/functions.html\\n‘, ‘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‘\\xd6\\xd0\\xb9\\xfa‘, ‘__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