有一個小程序想問問大家的

jack-1991

是書中的一個範例
我不太清楚這範例的目的要訓練甚麼的??
或者他想説明甚麼的??


輸出結果
ni
ni
84
84
100
120
g g g g g g g
a b c d e f g
a b c d e f g



def simple():
    spam = 'ni'
    def action():
        print(spam)          # name maps to enclosing function
    return action

act = simple()              # make and return nested function
act()                           # then call it: prints 'ni'




def normal():
    def action():
        return spam         # really, looked up when used
    spam = 'ni'
    return action

act = normal()
print(act())                # also prints 'ni'




def weird():
    spam = 42
    return (lambda: spam * 2)       # remembers spam in enclosing scope

act = weird()
print(act())    # prints 84




def weird():
    tmp = (lambda: spam * 2)        # remembers spam
    spam = 42                       # even though not set till here
    return tmp

act = weird()
print(act())                        # prints 84




def weird():
    spam = 42
    handler = (lambda: spam * 2)     # func doesn't save 42 now
    spam = 50
    print(handler())                 # prints 100: spam looked up now
    spam = 60
    print(handler())                 # prints 120: spam looked up again now

weird()




def odd():
    funcs = []
    for c in 'abcdefg':
       funcs.append((lambda: c))      # c will be looked up later
    return funcs                      # does not remember current c

for func in odd():
    print(func(), end=' ')            # print 7 g's, not a,b,c,... !




print()
def odd():
    funcs = []
    for c in 'abcdefg':
       funcs.append((lambda c=c: c))    # force to remember c now
    return funcs                        # defaults eval now

for func in odd():
    print(func(), end=' ')              # OK: now prints a,b,c,...




print()
funcs = []                              # enclosing scope is module
for c in 'abcdefg':                     # force to remember c now
   funcs.append((lambda c=c: c))        # else prints 7 g's again

for func in funcs:
    print(func(), end=' ')              # OK: prints a,b,c,...

timespace

没有任何说明就冒出一堆范例？这书的名字叫什么，要声讨！

Shell_HAT

铜球书名

supersuper8

首先要弄明白的是，搂住在看到什么内容的时候看到的这个范例吧？
然后再根据他看到的内容，来说吧?

jack-1991

Oreilly出版社 書名Programming Python
這是gui章節中的  説明這program的標題是這樣寫的: But you must still sometimes use defults instead of enclosing scope

supersuper8

回复 5# jack-1991


就这样一句？ 前面应该还有吧。这个应该是讲和闭包(Closure)有关的问题。

jack-1991

同一個programming 用幾個方法去達成從而説明分別...
大約是這様的

1: argument versus globals

2 passing in enclosing scope values with default arguments

3: passing in enclosing scope values with automatic references

4: But you must still sometimes use defults instead of enclosing scope

jack-1991

不過真的謝謝你這麼用心的幫助!!