blog.gladis.org

[2014-11-26] Porting python 2 code to python 3

I needed to profile a python 3 script of mine. During this process if wanted to use a great helper script but it was not compatible with mine, so i had to port it to python 3. Porting python 2 code to python 3 is really easy, thanks to 2to3. The last time i ported a library all I had to do was to call 2to3 -w and it worked.

This time it didn't worked as smoothly, but it was very easy to change the last bits. The whole process took no longer than 5 minutes.

The first step was to run 2to3.

2to3 -w lsprofcalltree.py

After I tried to run the code, I got two NameError messages.

NameError: name 'execfile' is not defined
NameError: name 'file' is not defined

The file problem was a really easy fix, all I neede to do was replace it with file

@@ -112,12 +112,12 @@ def main(args):
         except SystemExit:
             pass
     finally:
         kg = KCacheGrind(prof)
-        kg.output(file(options.outfile, 'w'))
+        kg.output(open(options.outfile, 'w'))

 if __name__ == '__main__':

The second change was a little bit bigger. Since execfile was inside a string that got evaluatet, 2to3 didn't catch this change. I created an empty new python file with just an execfile statement run 2to3 to see how the new output looked and applied those changes to the new file.

@@ -108,12 +108,12 @@ def main(args):
     prof = cProfile.Profile()
     try:
         try:
-            prof = prof.run('execfile(%r)' % (sys.argv[0],))
+            prof = prof.run("exec(compile(open(%r).read(), %r, 'exec'))" % (sys.argv[0],sys.argv[0]))
         except SystemExit:
             pass
     finally:
         kg = KCacheGrind(prof)

You can see all the different versions after each step and the final result at github. And the best, it's MIT licensed.