关于参数
Arbitrary Positional Arguments
- 任意位置参数，在一个位置参数前面添加星号
def say_hi(*names):
for name in names:
print(f'Hi, {name}!')
say_hi()
say_hi('ann')
say_hi('mike', 'john', 'zeo')
函数内部把names当作一个容器进行处理，所以可以传入任意容器：
list tuple dict set iterator generator
注：调用时容器前需要添加*
Arbitrary Keyword Argument
- 任意关键字参数
def say_hi(**names_greetings):
for name, greeting in names_greetings.items():
print(f'{greeting}, {name}!')
a_dictionary = {'mike':'Hello', 'ann':'Oh, my darling', 'john':'Hi'}
say_hi(**a_dictionary)
say_hi(**{'mike':'Hello', 'ann':'Oh, my darling', 'john':'Hi'})
注：调用时字典前添加**
参数列表中参数类型顺序
Order of Arguments
1.Positional
2.Arbitrary Positional
3.Keyword
4.Arbitrary Keyword
检测的时候从函数的参数列表开始检测，如果第一个参数是位置参数，则无论如何会将传递进来的第一个形参赋值给位置参数
def say_hi(*names, greeting='Hello', capitalized=False):
for name in names:
if capitalized:
name = name.capitalize()
print(f'{greeting}, {name}!')
# say_hi('mike', 'john', 'zeo')
say_hi('mike', 'yiya','Hi','asd',greeting='hi')
注：上例中greeting是可选参数
函数工具
- DIG
Iterator
- pyhon中所有的容器，都是用for…in…进行循环遍历
- 内建函数iter()可以把对象转换为可迭代对象，即支持for…in…和next()语句
a = {'1':'a','2':'b'}
h = iter(a)
a[next(h)]
a[next(h)]
创建迭代器
class Counter(object):
def __init__(self, start, stop):
self.current = start
self.stop = stop
# 约定俗成的写法
def __iter__(self):
return self
def __next__(self):
if self.current > self.stop:
raise StopIteration
else:
c = self.current
self.current += 1
return c
c = Counter(201, 203)
注：迭代器是一个类，它的每一个对象都是一个可迭代的对象
Generator
- 支持for…in…和next()语句
生成器函数
def counter(start, stop):
while start <= stop:
yield start
start += 1
for i in counter(101, 105):
print(i)
类实现__iter___方法
class Itercounter():
def __init__(self, start, stop):
self.start = start
self.stop = stop
def __iter__(self):
while self.start <= self.stop:
yield self.start
self.start += 1
print(sum(Itercounter(101, 105)))
生成器表达式
even = (e for e in range(10) if not e % 2)
生成器表达式代替列表推导式
- 当输入数据较大的时候，列表推导式可能会占用较大内存
- 通过next(g)方法可以依次产生输出值，避免内存用量问题
Decorator
- 装饰器是一个函数，对某个函数进行包装，返回包装后的函数
- 用来改变函数的行为
def a_decorator(func):
def wrapper():
print('We can do sth. before calling a_func...')
func()
print('... and we can do sth. after it was called...')
return wrapper
@a_decorator
def a_func():
print("Hi, I'm a_func!")
a_func()
Decorator Wiki
https://wiki.python.org/moin/PythonDecoratorLibrary#Memoize
正则表达式
-
常用表达式
- matching username
/^[a-z0-9_-]{3,16}$/ - matching password
/^[a-z0-9_-]{6,18}$/ - matching a HEX value
[/^#?([a-f0-9]{6}|[a-f0-9]{3})$/] - matching a slug
/^[a-z0-9-]+$/ - matching email address
[/^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/] - matching a URL
[/^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$/] - matching an IP address
/^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/ - matching a HTML tag
/^<([a-z]+)([^<]+)*(?:>(.*)<\/\1>|\s+\/>)$/
转载：https://blog.csdn.net/qq_41809896/article/details/101474245
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