Python - mechanism to identify compressed file type and uncompress

Question

A compressed file can be classified into below logical groups
a. The operating system which you are working on (*ix, Win) etc.
b. Different types of compression algo

Answer 1

This is a complex question that depends on a number of factors: the most important being how portable your solution needs to be.

The basics behind finding the file type given a file is to find an identifying header in the file, usually something called a "magic sequence" or signature header, which identifies that a file is of a certain type. Its name or extension is usually not used if it can be avoided. For some files, Python has this built in. For example, to deal with .tar files, you can use the tarfile module, which has a convenient is_tarfile method. There is a similar module named zipfile. These modules will also let you extract files in pure Python.

For example:

f = file('myfile','r')
if zipfile.is_zipfile(f):
    zip = zipfile.ZipFile(f)
    zip.extractall('/dest/dir')
elif tarfile.is_tarfile(f):
    ...

If your solution is Linux or OSX only, there is also the file command which will do a lot of the work for you. You can also use the built-in tools to uncompress the files. If you are just doing a simple script, this method is simpler and will give you better performance.