check interpreter version before running script

[Fredrik Lundh]

"rbt" <rbt at athop1.ath.vt.edu> wrote:

> Is there a recommended or 'Best Practices' way of checking the version of python before running 
> scripts? I have scripts that use the os.walk() feature (introduced in 2.3) and users running 2.2 
> who get errors. Instead of telling them, 'Upgrade you Python Install, I'd like to use sys.version 
> or some other way of checking before running.

if you depend on os.walk, check for os.walk.

    try:
        from os import walk
    except ImportError:
        print "sorry, you need a newer python version!"
        sys.exit()

or

    import os
    try:
        os.walk
    except AttributeError:
        print "sorry, you need a newer python version!"
        sys.exit()

if you only depend on a few functions, you can usually emulate them in
earlier versions.  if 2.2 or newer is a reasonable requirement, you can
put a copy of the walk function in your script:

    from __future__ import generators
    try:
        from os import walk
    except ImportError:
        def walk(...):
            # copied from os.py in 2.3

if you want to support e.g 1.5.2 or newer, you can use something like this:

    import os
    try:
        from os import walk
    except ImportError:
        class walk:
            def __init__(self, directory):
                self.stack = [directory]
            def __getitem__(self, index):
                dirpath = self.stack.pop(0)
                dirnames = []
                filenames = []
                for file in os.listdir(dirpath):
                    name = os.path.join(dirpath, file)
                    if os.path.isdir(name) and not os.path.islink(name):
                        dirnames.append(file)
                        self.stack.append(name)
                    else:
                        filenames.append(file)
                return dirpath, dirnames, filenames

(tweak as necessary)

</F>