Import error in python

Question

In file1.py:

 def test1():
 print "hi"

In file2.py:

 from file1 import test1
 def test2():
 print "hello"
 test1()
 test2()

Output:

 hi
 hello

Now in file 1 if i include test2 i get the following error:

 from file2 import test2
 def test1():
 print "hi"
 Traceback (most recent call last):
 File "file1.py", line 1, in ?
 from file2 import test2
 File "/root/pyt/file2.py", line 1, in ?
 from file1 import test1
 File "/root/pyt/file1.py", line 1, in ?
 from file2 import test2
 ImportError: cannot import name test2

Can some explain why and how to make it work?

• Noufal Ibrahim: Please preview your question before submitting it. It was quite unreadable.
• SilentGhost: cyclic import, read all about it.

Answer 1

This is a circular import problem. You are importing file2 from file1 and then at the top level of file2, importing file1 again. This means that 1 cannot load unless you import 2 and 2 cannot load unless you import `1.

As for how to make it work, can you explain what you want to do? Why don't you just put both these functions in the same module and import that in a single go?

• Ignacio Vazquez-Abrams: No, not this either. Circular imports are valid in Python. What isn't valid is accessing attributes that don't exist.

Answer 2

The name doesn't exist in the module by the time you try to access it.

• Noufal Ibrahim: I don't think so. The error is not an AttributeError. It's an ImportError. The module couldn't be imported because of the cyclic dependency.
• Ignacio Vazquez-Abrams: @Noufal: It's only an ImportError because the attribute is being specified in an import operation. Any non-existent name will give this.
• Rajeev: Vazquez-Abram:If we pass parameters to functions and check whether to import or not,then will it work
• Ignacio Vazquez-Abrams: @Rajeev: It will work if the attribute you're accessing exists at that time.