PyCharm中的子包和相关进口

Question

I am using python 2:

python --version
Python 2.7.13 :: Continuum Analytics, Inc.

I have the following project structure:

.
└── foo
    ├── bar1
    │   ├── __init__.py
    │   └── mod1.py
    ├── bar2
    │   ├── __init__.py
    │   └── mod2.py
    ├── __init__.py
    └── start.py

start.py

from foo.bar2.mod2 import mod2_f
mod2_f()

mod1.py

def mod1_f():
    print "mod1_f"

mod2.py

from foo.bar1.mod1 import mod1_f

def mod2_f():
    mod1_f()
    print "mod2_f"

If I run start.py from an IDE things work ok.

However using something like this:

python ./foo/start.py

results in

Traceback (most recent call last):
  File "./foo/start.py", line 1, in <module>
    from foo.bar2.mod2 import mod2_f
ImportError: No module named foo.bar2.mod2

Now, let's say I change the imports to

start.py

from bar2.mod2 import mod2_f
mod2_f()

mod2.py

from bar1.mod1 import mod1_f

def mod2_f():
    mod1_f()
    print "mod2_f"

Now things work from the command line python ./foo/start However, PyCharm complains. why these differences?

Answer 1

foo is the directory which contains everything, including start.py

So when from start.py you do this

from foo.bar2.mod2 import mod2_f

python looks for a foo module ( foo is a module because it contains __init__.py ), which too high in your directory structure. I suppose it works from the IDE because IDE adds every module directory to pythonpath. But not from command line it doesn't.

simple fix since bar2 is a directory at the same level as start.py :

from bar2.mod2 import mod2_f

note that from works differently in python 3. See ImportError on python 3, worked fine on python 2.7 , that's probably why PyCharm complains when fixing the import line. You should configure PyCharm so it uses Python 2 and not Python 3 for it to work, or just drop the from syntax altogether and do:

import bar2.mod2.mod2_f