Searching for equivalent of FileNotFoundError in Python 2

If FileNotFoundError isn't there, define it:

try:
    FileNotFoundError
except NameError:
    FileNotFoundError = IOError

Now you can catch FileNotFoundError in Python 2 since it's really IOError.

Be careful though, IOError has other meanings. In particular, any message should probably say "file could not be read" rather than "file not found."

The Python 2 / 3 compatible way to except a FileNotFoundError is this:

import errno

try:
    with open('some_file_that_does_not_exist', 'r'):
        pass
except EnvironmentError as e:
    if e.errno != errno.ENOENT:
        raise

Other answers are close, but don't re-raise if the error number doesn't match.

Using IOError is fine for most cases, but for some reason os.listdir() and friends raise OSError instead on Python 2. Since IOError inherits from OSError it's fine to just always catch OSError and check the error number.

Edit: The previous sentence is only true on Python 3. To be cross compatible, instead catch EnvironmentError and check the error number.

You can use the base class exception EnvironmentError and use the 'errno' attribute to figure out which exception was raised:

from __future__ import print_function

import os
import errno

try:
    open('no file of this name')   # generate 'file not found error'
except EnvironmentError as e:      # OSError or IOError...
    print(os.strerror(e.errno))  

Or just use IOError in the same way:

try:
    open('/Users/test/Documents/test')   # will be a permission error
except IOError as e:
    print(os.strerror(e.errno))  

That works on Python 2 or Python 3.

Be careful not to compare against number values directly, because they can be different on different platforms. Instead, use the named constants in Python's standard library errno module which will use the correct values for the run-time platform.