Re: Why don't isdir() and isfile() work for me?

Hi Ray,

A couple of tips to ease your Python journey:

1. Learn how to use pip, virtualenv
<http://www.saltycrane.com/blog/2009/05/notes-using-pip-and-virtualenv-django/>,
and virtualenvwrapper
<http://www.doughellmann.com/projects/virtualenvwrapper/>. You can have
any number of different versions of Python and modules in their own
isolated virtual environments that way. You can't always rely on the
Python packages provided by your distro because first, not every
potential Python module is packaged by your distro, and second, they may
lag, and finally, you may need some bleeding edge packages checked
straight out of svn, git, or hg sometimes.

2. Install and use ipython <http://ipython.scipy.org/moin/>. It's an
alternative to the standard Python shell and offers some very useful
features, such as shell completion, history, macros. See below how you
could have figured out the answer to your question in a matter of
seconds. (I've read good things about another shell, bpython
<http://bpython-interpreter.org/> but I haven't used it.)

cilkay@jupiter:~$ ipython
Python 2.6.2 (r262:71600, Jan 25 2010, 18:46:47)
Type "copyright", "credits" or "license" for more information.

IPython 0.10 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object'. ?object also works, ?? prints more.

In [1]: import os

# I typed os.is and hit the tab key and got:

In [2]: os.isatty
Out[2]: <built-in function isatty>

# That told me that islink and isfile aren't functions of os. Let's get
some help.

In [3]: os?
Type: module
Base Class: <type 'module'>
String Form: <module 'os' from
'/home/cilkay/projects/virtualenvs/ptag_django_cms/lib64/python2.6/os.pyc'>
Namespace: Interactive
File:
/home/cilkay/projects/virtualenvs/ptag_django_cms/lib64/python2.6/os.py
Docstring:
OS routines for Mac, NT, or Posix depending on what system we're
on.

This exports:
- all functions from posix, nt, os2, or ce, e.g. unlink, stat, etc.
- os.path is one of the modules posixpath, or ntpath
- os.name is 'posix', 'nt', 'os2', 'ce' or 'riscos'
- os.curdir is a string representing the current directory ('.'
or ':')
- os.pardir is a string representing the parent directory ('..'
or '::')
- os.sep is the (or a most common) pathname separator ('/' or ':'
or '\\')
- os.extsep is the extension separator ('.' or '/')
- os.altsep is the alternate pathname separator (None or '/')
- os.pathsep is the component separator used in $PATH etc
- os.linesep is the line separator in text files ('\r' or '\n' or
'\r\n')
- os.defpath is the default search path for executables
- os.devnull is the file path of the null device ('/dev/null', etc.)

Programs that import and use 'os' stand a better chance of being
portable between different platforms. Of course, they must then
only use functions that are defined by all platforms (e.g., unlink
and opendir), and leave all pathname manipulation to os.path
(e.g., split and join).


# os.path looks like a good candidate so let's try typing that and "is"
and hitting tab

In [4]: os.path.is
os.path.isabs os.path.isdir os.path.isfile os.path.islink
os.path.ismount

# If you want more help:

In [4]: os.path.isdir?
Type: function
Base Class: <type 'function'>
String Form: <function isdir at 0x7f301e3adb18>
Namespace: Interactive
File:
/home/cilkay/projects/virtualenvs/ptag_django_cms/lib64/python2.6/genericpath.py
Definition: os.path.isdir(s)
Docstring:
Return true if the pathname refers to an existing directory.



In [5]:

It's quite interactive and productive. You have access to bash from
within ipython too and when you exit, your ipython history is saved,
just like bash history.

The Python lists are quite busy, by the way, and irc.freenode.net
#python is also an excellent resource.
--
Regards,

Clifford Ilkay
Dinamis
1419-3266 Yonge St.
Toronto, ON
Canada M4N 3P6

<http://dinamis.com>
+1 416-410-3326

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