导入时模块执行两次！ [英] Module executed twice when imported!
问题描述
它似乎是Python的一个不变量（只要Python具有不变量）
模块在Python会话中最多执行一次。我有一个
相当古怪的例子打破了这个不变量：任何人都可以启发
我发生了什么事情？
--- test.py ---
import imptest
execfile（''subtest.py''，dict（__ name__ =''subtest.py''））
--- imptest.py ---
打印''Imptest进口''
--- subtest.py ---
导入imptest
---
$ python test.py
Imptest导入
Imptest进口
$
嗯。如果字典中省略了值__name__，或者它的
值至少不匹配''subtest。''则该消息仅打印
一次（例如，传递dict（__ name __ =''subtest''）会产生一个
导入消息）。
这两种情况都发生在python 2.4和2.3。我不明白。
It seems to be an invariant of Python (insofar as Python has invariants)
that a module is executed at most once in a Python session. I have a
rather bizzare example that breaks this invariant: can anyone enlighten
me as to what is going on?
--- test.py ---
import imptest
execfile(''subtest.py'', dict(__name__ = ''subtest.py''))
--- imptest.py ---
print ''Imptest imported''
--- subtest.py ---
import imptest
---
$ python test.py
Imptest imported
Imptest imported
$
Hmm. If the value __name__ is omitted from the dictionary, or if its
value doesn''t match at least ''subtest.'' then the message is printed only
once (for example, passing dict(__name__=''subtest'') produces one
"imported" message).
This happens with both python 2.4 and 2.3. I don''t get it.
推荐答案
python test.py
Imptest进口
Imptest进口
python test.py
Imptest imported
Imptest imported
嗯。如果字典中省略了值__name__，或者它的
值至少不匹配''subtest。''则该消息仅打印
一次（例如，传递dict（__ name __ =''subtest''）会产生一个
导入消息）。
这两种情况都发生在python 2.4和2.3。我得不到它。
Hmm. If the value __name__ is omitted from the dictionary, or if its
value doesn''t match at least ''subtest.'' then the message is printed only
once (for example, passing dict(__name__=''subtest'') produces one
"imported" message).
This happens with both python 2.4 and 2.3. I don''t get it.
Michael Abbott写道：
Michael Abbott wrote:
它似乎是Python的一个不变量（因为Python有不变量）
一个模块在Python会话中最多执行一次。我有一个相当古怪的例子打破了这个不变量：任何人都可以告诉我发生了什么事吗？
--- test.py ---
import imptest
execfile（''subtest.py''，dict（__ name__ =''subtest.py''））
--- imptest.py ---
print'' Imptest导入''
--- subtest.py ---
导入imptest
---
It seems to be an invariant of Python (insofar as Python has invariants)
that a module is executed at most once in a Python session. I have a
rather bizzare example that breaks this invariant: can anyone enlighten
me as to what is going on?
--- test.py ---
import imptest
execfile(''subtest.py'', dict(__name__ = ''subtest.py''))
--- imptest.py ---
print ''Imptest imported''
--- subtest.py ---
import imptest
---
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