在Python中使用3to2，得到“ python：无法打开文件'3to2'：[Errno 2]没有这样的文件或目录”

Question

I have installed 3to2-1.1.1 on my system (found here ), cd'd to the directory of my test file (a simple "Hello, world!" program written in 3 syntax) Typed into my command prompt:

python 3to2 HelloWorld.py

With the following output:

python: can't open file '3to2': [Errno 2] No such file or directory

I attempted to change the directory name/path, but after looking over this post, I'm convinced it may be a dependency issue?

I have raised an issue on the creator's repo, and searched endlessly on the interwebs, but seem to be the only person in the world experiencing this issue.

I have tried uninstalling and re-installing just...so many ways. Any and all help appreciated - even if you just tell me it's operator error.

Extra notes:

• I am running Python 2.7 (but also tried installing and running this with 3)
• I am using a Windows cmd

Answer 1

Windows cannot take care of shebangs. The default association in Windows is through file extensions. However, the file 3to2 does not come with a .py extension (only a shebang). As a result Windows is usually unable to determine what to do with the file.

OP discussed the following use cases:

• python 3to2 <arg-file> . This doesn't work for me in a pip install. Python throws an internal ENOENT (I/O) error. This use case is discarded.
• 3to2 <arg-file> . Doesn't work either. This is because Windows doesn't know how to execute this file. Funnily enough Windows cannot find the file even though its location is in the system PATH . Calling where gives negative results. Windows is not able to handle filenames without extensions, somehow.
• Rename 3to2 to 3to2.py (in %PYTHON_INSTALL_DIRECTORY%\\Scripts\\ ) since it really is a python source file. Python on Windows is set up to handle .py file by default. The location of the file is in the system PATH . Try calling 3to2.py <arg-file> . This works!
• Returning to the first case: After renaming, try calling python 3to2.py <arg-file> . Still doesn't work. Python throws an ENOENT error.

In conclusion, renaming the file 3to2.py is a hack that works. The dependent programs might not work.

---

Don't give up just yet!

So why did calling 3to2.py through Python fail? The answer is simple. Python only calls what you give it. When you specify a relative path, it will only look in the current working directory of the program and no more. When you give an absolute path, Python does the needful.

---

NOTES:

• I only installed the package through pip only. I did not test through any other methods.
• I tested this on a Windows 7 SP1 system. Newer versions may have better filesystem support.

Answer 2

I tried install it via pip on my Linux, it works out-of-the-box.

However, you could just use it like 2to3 . So type 3to2 -w HelloWorld.py in cmd maybe works. If cmd can't find the path of 3to2 , then you need to find it manually.

kevin@Arch ~> cat 1.py 
print('Hello')
var = input('text')


kevin@Arch ~> 3to2 1.py
RefactoringTool: Skipping optional fixer: collections
RefactoringTool: Skipping optional fixer: int
RefactoringTool: Skipping optional fixer: memoryview
RefactoringTool: Skipping optional fixer: printfunction
RefactoringTool: Skipping optional fixer: unittest
RefactoringTool: Refactored 1.py
b'--- 1.py\t(original)'
b'+++ 1.py\t(refactored)'
b'@@ -1,2 +1,2 @@'
b"-print('Hello')"
b"-var = input('text')"
b"+print u'Hello'"
b"+var = raw_input(u'text')"
RefactoringTool: Files that need to be modified:
RefactoringTool: 1.py


kevin@Arch ~> 3to2 -w 1.py
RefactoringTool: Skipping optional fixer: collections
RefactoringTool: Skipping optional fixer: int
RefactoringTool: Skipping optional fixer: memoryview
RefactoringTool: Skipping optional fixer: printfunction
RefactoringTool: Skipping optional fixer: unittest
RefactoringTool: Refactored 1.py
b'--- 1.py\t(original)'
b'+++ 1.py\t(refactored)'
b'@@ -1,2 +1,2 @@'
b"-print('Hello')"
b"-var = input('text')"
b"+print u'Hello'"
b"+var = raw_input(u'text')"
RefactoringTool: Files that were modified:
RefactoringTool: 1.py


kevin@Arch ~> cat 1.py 
print u'Hello'
var = raw_input(u'text')
kevin@Arch ~> 

Answer 3

After installing on another system, I have not been able to replicate the issue. this makes me believe that something is wrong on my side of things. I will update here if I ever figure it out.