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标题: python-张荣亮-2021.01.21 [打印本页]
作者: 张荣亮 时间: 2021-1-22 09:03
标题: python-张荣亮-2021.01.21
'''生成器generator'''
l =[x*x for x in range(10)]
print(l)
# 实现生成器
t =(x*x for x in range(10))
print(t)
# 使用next()方法，可以获取生成式中的下一个元素
# 如果生成器中的元素已经取完了，则抛出StopIteration异常
# print(next(t))
print('----------------------------------')
g = (x*x for x in range(10))
for i in g:
print(i)
'''
利用函数实现生成器
'''
import time
# 自然数序列
def nature():
n = 1
while True:
'''
return n 1.返回n的值；2.立即结束函数的执行
yield n 1.返回n的值；2.立即暂停函数的执行
'''
# print(n)
yield n
n += 1
g = nature()
# print(next(g))
# print(next(g))
# print(next(g))
# print(next(g))
# print(next(g))
for e in g:
print(e)
time.sleep(1)
# 利用生成器生成斐波那契数列序列
'''
1 1 2 3 5 8 13
a = 0 b = 1 a+b = 1; a = b b = a+b
a = 1 b = 1 a+b = 2; a = b b = a+b
a = 1 b = 2 a+b = 3; a = b b = a+b
a = 2 b = 3 a+b = 5; a = b b = a+b
a = 3 b = 5 a+b = 8; a = b b = a+b
'''
def fib():
a,b = 0,1
while True:
yield b
# t = a
# a = b
# b = t+b
# 先计算赋值符号的右边，然后再赋值
a,b = b,a+b
f = fib()
print(f)
print(fib)
for i in f:
print(i)
time.sleep(0.5)
'''
高阶函数
函数名本质就是一个指向该函数的变量
'''
print(abs(-5))
print(abs)
f = abs
print(f(-5))
abs = 7
print(abs)
# print(abs(-5))
'''
函数作为参数传入
一个函数A可以接收另一个函数B作为参数，我们把这个函数A称我高阶函数
'''
def add(x,y,f):
return f(x)+f(y)
print(add(3,4,f))
print(add(-3,-4,f))
def g(x):
return x*x
print(add(3,4,g))
# map()函数 /reduce()/filter()
r = map(g,[1,2,3,4,5])
print(list(r))
'''
函数作为返回值
'''
def s(*args):
ss = 0
for arg in args:
ss += arg
return ss
print(s(1,2,3,4))
print(s(1,3,5,7))
'''
lazy_s()函数中定义了内部函数s()，而s()函数中又引用了外部函数lazy_s()的参数 args
当lazy_s()函数返回函数s(),相关的参数和变量都已经保存在返回的函数中
我们把这种程序结构称为 闭包Closure
'''
def lazy_s(*args):
# 定义函数
def s():
ss = 0
for arg in args:
ss += arg
return ss
return s
h = lazy_s(1,2,3,4)
'''
def s():
ss = 0
for arg in (1,2,3,4):
ss += arg
return ss
'''
print(h)
print(h())
'''
装饰器Decorator
在代码运行期间动态增加功能的方式，就称为装饰器
'''
# 创建一个装饰器
def log(func):
'''
func:将要被装饰的函数
'''
def wrapper(*args,**kw):
print('调用函数:%s'%func.__name__)
return func(*args,**kw)
return wrapper
import time
# now = log(now)
# now()
@log
def now():
# print('调用函数:%s'%now.__name__)
print(time.strftime('%Y-%m-%d %H:%M:%S'))
now()
# print(now)
# print(now.__name__)
# now.__name__ = '现在'
# print(f.__name__)
import functools
# 可以传参的装饰器
def log2(text):
def decorator(func):
@functools.wraps(func)
def wrapper(*args,**kw):
# wrapper.__name__ = func.__name__
print('%s:%s'%(text,func.__name__))
return func(*args,**kw)
return wrapper
return decorator
@log2('马上立刻执行函数') # now2 log2('马上立刻执行函数')(now2)
def now2():
# print('调用函数:%s'%now.__name__)
print(time.strftime('%Y-%m-%d %H:%M:%S'))
now2()
print(now2.__name__)
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