作业

3.处理文件，用户指定要查找的文件和内容，将文件中包含要查找内容的每一行都输出到屏幕

def func(filename,text):
    with open(filename,encoding="utf-8") as f:
        for i in f:
            if text in i:
                yield  i

fil = func("1","wu")
---------------------
for i in fil:
    print(i.strip())
----------------------
print(next(fil))
print(next(fil))
=======================

--------------------------------------------------------------------------------------------------------------------------------

def demo():
    for i in range(4):
        yield i

g=demo()

g1=(i for i in g)
g2=(i for i in g1)

print(list(g1))
print(list(g2))　　#因g1已经将demo取完，所以会输出[]
---------------------------
output

[0, 1, 2, 3]
[]

---------------------------------------------------------------------------------

def test():
    for i in range(4):
        yield i

g=test()
for n in [1,10]:
    g=(add(n,i) for i in g)
"""
当n=10时，生成器g并没有执行，所以g执行时n=10
"""

print(list(g))
"""
开始执行个g，(add(n,i) for i in g)等价于(add(n,i) for i in (add(n,i) for i in text()))
                                     (add(n,i) for i in (10,11,12,13))
"""
-----------------------------------------------------------------------------------
output
[20, 21, 22, 23]