Python – Associate file extension to python script, so that I can open the file by double click, in windows

file extensionfile-associationpythonwindows

I want to do the following:

Save numeric data in a CSV-like formatting, with a ".foo" extension;
Associate the ".foo" file extension with some python script, which in turns opens the .foo file, reads its content, and plots something with a plotting library (matplotlib most probably).

The use-case would be: double-click the file, and its respective plot pops up right away.

I wonder how I should write a python script in order to do that.
Besides, the windows "open with" dialog only allows me to choose executables (*.exe). If I choose "fooOpener.py", it doesn't work.

Best Answer

This isn't really a programming question, but what you need to do is to figure out how to get the Python executable into the registry key that opens your data file.

For example, I created a little Python script called opener.py that looks like this:

import sys
print(sys.argv)
input()

Then I created a testfile.foo and used the "change" button in that file's property dialog to choose opener.py. (You can do this if you click Browse and change the Open With dialog's file filter to "All Files".)

Of course this didn't work (as you noticed). So I opened regedit and searched for opener.py and found it at the following registry key:

HKEY_CURRENT_USER\Software\Classes\Applications\opener.py\shell\open\command

The default value of this key was "C:\opener.py" %1. I changed it to python "C:\opener.py" %1. It worked!

Long story short, to do this properly you need to custom-edit the registry. Actually setting up the file association is more complex than just editing that one key (you have to also indicate that .foo is associated with opener.py).

An alternative approach would be to turn your Python script into a standalone executable using one of the several tools available for that purpose, or write a small executable in C that launches the script.

Related Solutions

Python – How to you profile a Python script

Python includes a profiler called cProfile. It not only gives the total running time, but also times each function separately, and tells you how many times each function was called, making it easy to determine where you should make optimizations.

You can call it from within your code, or from the interpreter, like this:

import cProfile
cProfile.run('foo()')

Even more usefully, you can invoke the cProfile when running a script:

python -m cProfile myscript.py

To make it even easier, I made a little batch file called 'profile.bat':

python -m cProfile %1

So all I have to do is run:

profile euler048.py

And I get this:

1007 function calls in 0.061 CPU seconds

Ordered by: standard name
ncalls  tottime  percall  cumtime  percall filename:lineno(function)
    1    0.000    0.000    0.061    0.061 <string>:1(<module>)
 1000    0.051    0.000    0.051    0.000 euler048.py:2(<lambda>)
    1    0.005    0.005    0.061    0.061 euler048.py:2(<module>)
    1    0.000    0.000    0.061    0.061 {execfile}
    1    0.002    0.002    0.053    0.053 {map}
    1    0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler objects}
    1    0.000    0.000    0.000    0.000 {range}
    1    0.003    0.003    0.003    0.003 {sum}

EDIT: Updated link to a good video resource from PyCon 2013 titled Python Profiling
Also via YouTube.

Python – How to get the filename without the extension from a path in Python

Getting the name of the file without the extension:

import os
print(os.path.splitext("/path/to/some/file.txt")[0])

Prints:

/path/to/some/file

Documentation for os.path.splitext.

Important Note: If the filename has multiple dots, only the extension after the last one is removed. For example:

import os
print(os.path.splitext("/path/to/some/file.txt.zip.asc")[0])

Prints:

/path/to/some/file.txt.zip

See other answers below if you need to handle that case.

Best Answer

Related Solutions

Python – How to you profile a Python script

Python – How to get the filename without the extension from a path in Python

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