File extension validation with python

Question

I want to check if a given file's extension is correct or not. For example, someone give me a file with an extension .zip but actually it may be an executable.

Using mimetypes I could not determine a file's real type. As far as I see, mimetypes needs an extension.

I can map the output of unix file command with some extensions. Even if you change the extension, you cannot deceive file command. However, this solution needs a subprocess.

I thought, there may be a more pythonic solution of this problem. Does anyone know?

@JesseJ It is no problem to me. It may be handled as text file. I want to seperate archive, executable, library etc. — Ricardo Cristian Ramirez, Aug 30 '13 at 21:11

KurzedMetal · Accepted Answer · 2013-08-30T21:36:26.127

1

Searching the name of the C library (libmagic) used for the file command, nets 3 interesting python packages on PyPI:

libmagic (bitbucket repo)
python-magic (you can find some documentation in the github repo)
filemagic (github repo)

edited Aug 30 '13 at 21:36

answered Aug 30 '13 at 21:26

KurzedMetal

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score 0 · Answer 2 · answered Aug 30 '13 at 21:08

Ultimately, there is no absolute way of knowing. For several reasons:

Some file format use simple identifiers, but others don't.
For those that don't, the only way is analyzing the behavior of a program able to able the format. If the program can successfully open the file, then it belongs to it.
But if not, the file could belong to hundreds of formats you don't have a program to open with.

I'm afraid you will need to be content with a partial answer like the ones you already have.

File extension validation with python

2 Answers2