newb question: file searching

[jaysherby@gmail.com]

I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories. Can someone
set me on the right path to what modules and calls to use to do that?
You'd think that it would be a fairly simple proposition, but I can't
find examples anywhere. Thanks.

[godavemon]

Re: newb question: file searching

Hey, I've done similar things.

You can use system comands with the following

import os
os.system('comm and here')

You'd maybe want to do something like

dir_name = 'mydirectory'
import os
os.system('ls ' +dir_name + ' lsoutput.tmp')
fin = open('lsoutput. tmp', 'r')
file_list = fin.readlines()
fin.close()

Now you have a list of all the files in dir_name stored in file_list.

Then you'll have to parse the input with string methods. They're easy
in python. Here's the list of them:

http://docs.python.org/lib/string-methods.html

There is probably a better way to get the data from an os.system
command but i haven't figured it out. Instead what i'm doing is
writing the stdio output to a file and reading in the data. It works
fine. Put it in your tmp dir if you're in linux.


jaysherby@gmail .com wrote:

I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories. Can someone
set me on the right path to what modules and calls to use to do that?
You'd think that it would be a fairly simple proposition, but I can't
find examples anywhere. Thanks.

[godavemon]

Re: newb question: file searching

Hey, I've done similar things.

You can use system comands with the following

import os
os.system('comm and here')

You'd maybe want to do something like

dir_name = 'mydirectory'
import os
os.system('ls ' +dir_name + ' lsoutput.tmp')
fin = open('lsoutput. tmp', 'r')
file_list = fin.readlines()
fin.close()

Now you have a list of all the files in dir_name stored in file_list.

Then you'll have to parse the input with string methods. They're easy
in python. Here's the list of them:

http://docs.python.org/lib/string-methods.html

There is probably a better way to get the data from an os.system
command but i haven't figured it out. Instead what i'm doing is
writing the stdio output to a file and reading in the data. It works
fine. Put it in your tmp dir if you're in linux.


jaysherby@gmail .com wrote:

I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories. Can someone
set me on the right path to what modules and calls to use to do that?
You'd think that it would be a fairly simple proposition, but I can't
find examples anywhere. Thanks.

[Mike Kent]

Re: newb question: file searching


jaysherby@gmail .com wrote:

I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories.

What you want is os.walk().

http://www.python.org/doc/current/lib/os-file-dir.html

[hiaips]

Re: newb question: file searching

jaysherby@gmail .com wrote:

I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories. Can someone
set me on the right path to what modules and calls to use to do that?
You'd think that it would be a fairly simple proposition, but I can't
find examples anywhere. Thanks.

dir_name = 'mydirectory'
extension = 'my extension'
import os
files = os.listdir(dir_ name)
files_with_ext = [file for file in files if file.endswith(e xtension)]

That will only do the top level (not subdirectories) , but you can use
the os.walk procedure (or some of the other procedures in the os and
os.path modules) to do that.

--Dave

[jaysherby@gmail.com]

Re: newb question: file searching

Mike Kent wrote:

What you want is os.walk().
>
http://www.python.org/doc/current/lib/os-file-dir.html

I'm thinking os.walk() could definitely be a big part of my solution,
but I need a little for info. If I'm reading this correctly, os.walk()
just goes file by file and serves it up for your script to decide what
to do with each one. Is that right? So, for each file it found, I'd
have to decide if it met the criteria of the filetype I'm searching for
and then add that info to whatever datatype I want to make a little
list for myself? Am I being coherent?

Something like:

for files in os.walk(top, topdown=False):
for name in files:
(do whatever to decide if criteria is met, etc.)

Does this look correct?

[hiaips]

Re: newb question: file searching

I'm thinking os.walk() could definitely be a big part of my solution,
but I need a little for info. If I'm reading this correctly, os.walk()
just goes file by file and serves it up for your script to decide what
to do with each one. Is that right? So, for each file it found, I'd
have to decide if it met the criteria of the filetype I'm searching for
and then add that info to whatever datatype I want to make a little
list for myself? Am I being coherent?
>
Something like:
>
for files in os.walk(top, topdown=False):
for name in files:
(do whatever to decide if criteria is met, etc.)
>
Does this look correct?

IIRC, repeated calls to os.walk would implement a depth-first search on
your current directory. Each call returns a list:
[<directory name relative to where you started>, <list of files and
directories in that directory>]

--dave

[jaysherby@gmail.com]

Re: newb question: file searching

Thanks, Dave. That's exactly what I was looking for, well, except for
a few small alterations I'll make to achieve the desired effect. I
must ask, in the interest of learning, what is

[file for file in files if file.endswith(e xtension)]

actually doing? I know that 'file' is a type, but what's with the set
up and the brackets and all? Can someone run down the syntax for me on
that? And also, I'm still not sure I know exactly how os.walk() works.
And, finally, the python docs all note that symbols like . and ..
don't work with these commands. How can I grab the directory that my
script is residing in?

Thanks.


hiaips wrote:

jaysherby@gmail .com wrote:

I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories. Can someone
set me on the right path to what modules and calls to use to do that?
You'd think that it would be a fairly simple proposition, but I can't
find examples anywhere. Thanks.

>
dir_name = 'mydirectory'
extension = 'my extension'
import os
files = os.listdir(dir_ name)
files_with_ext = [file for file in files if file.endswith(e xtension)]
>
That will only do the top level (not subdirectories) , but you can use
the os.walk procedure (or some of the other procedures in the os and
os.path modules) to do that.
>
--Dave

[Jason]

Re: newb question: file searching


jaysherby@gmail .com wrote:

Mike Kent wrote:

What you want is os.walk().

http://www.python.org/doc/current/lib/os-file-dir.html

>
I'm thinking os.walk() could definitely be a big part of my solution,
but I need a little for info. If I'm reading this correctly, os.walk()
just goes file by file and serves it up for your script to decide what
to do with each one. Is that right? So, for each file it found, I'd
have to decide if it met the criteria of the filetype I'm searching for
and then add that info to whatever datatype I want to make a little
list for myself? Am I being coherent?
>
Something like:
>
for files in os.walk(top, topdown=False):
for name in files:
(do whatever to decide if criteria is met, etc.)
>
Does this look correct?

Not completely. According to the documentation, os.walk returns a
tuple:
(directory, subdirectories, files)
So the files you want are in the third element of the tuple.

You can use the fnmatch module to find the names that match your
filename pattern.

You'll want to do something like this:

>>for (dir, subdirs, files) in os.walk('.'):

.... for cppFile in fnmatch.filter( files, '*.cpp'):
.... print cppFile
....
ActiveX Test.cpp
ActiveX TestDoc.cpp
ActiveX TestView.cpp
MainFrm.cpp
StdAfx.cpp

>>>

Please note that your results will vary, of course.

[hiaips]

Re: newb question: file searching


jaysherby@gmail .com wrote:

Thanks, Dave. That's exactly what I was looking for, well, except for
a few small alterations I'll make to achieve the desired effect. I
must ask, in the interest of learning, what is
>
[file for file in files if file.endswith(e xtension)]
>
actually doing? I know that 'file' is a type, but what's with the set
up and the brackets and all? Can someone run down the syntax for me on
that? And also, I'm still not sure I know exactly how os.walk() works.
And, finally, the python docs all note that symbols like . and ..
don't work with these commands. How can I grab the directory that my
script is residing in?

[file for file in files if file.endswith(e xtension)] is called a list
comprehension. Functionally, it is equivalent to something like this:
files_with_ext = []
for file in files:
if file.endswith(e xtension):
files_with_ext. append(file)
However, list comprehensions provide a much more terse, declarative
syntax without sacrificing readability.

To get your current working directory (i.e., the directory in which
your script is residing):
cwd = os.getcwd()

As far as os.walk...
This is actually a generator (effectively, a function that eventually
produces a sequence, but rather than returning the entire sequence, it
"yields" one value at a time). You might use it as follows:
for x in os.walk(mydirec tory):
for file in x[1]:
<whatever tests or code you need to run>

You might want to read up on the os and os.path modules - these
probably have many of the utilities you're looking for.

Good luck,
dave

[hiaips]

Re: newb question: file searching

Oops, what I wrote above isn't quite correct. As another poster pointed
out, you'd want to do
for file in x[2]:
....

--dave

[jaysherby@gmail.com]

Re: newb question: file searching

So far, so good. I just have a few more questions.

Here's my code so far:

import os
top = '/home/USERNAME/'
images = []
for files in os.walk(top, topdown=True):
images += [file for file in files[2] if file.endswith(' jpg')]
print images

I still need to know how I can dynamically get the name of the
directory that my script is in. Also, how can I get it to add the full
path of the file to "images" instead of just the file name. See, when
I go to use a particular image name later on, it won't do me much good
if I don't have the path to it.

[Simon Forman]

Re: newb question: file searching

jaysherby@gmail .com wrote:

hiaips wrote:

jaysherby@gmail .com wrote:
I'm new at Python and I need a little advice. Part of the script I'm
trying to write needs to be aware of all the files of a certain
extension in the script's path and all sub-directories. Can someone
set me on the right path to what modules and calls to use to do that?
You'd think that it would be a fairly simple proposition, but I can't
find examples anywhere. Thanks.

dir_name = 'mydirectory'
extension = 'my extension'
import os
files = os.listdir(dir_ name)
files_with_ext = [file for file in files if file.endswith(e xtension)]

That will only do the top level (not subdirectories) , but you can use
the os.walk procedure (or some of the other procedures in the os and
os.path modules) to do that.

--Dave

>
Thanks, Dave. That's exactly what I was looking for, well, except for
a few small alterations I'll make to achieve the desired effect. I
must ask, in the interest of learning, what is
>
[file for file in files if file.endswith(e xtension)]
>
actually doing? I know that 'file' is a type, but what's with the set
up and the brackets and all? Can someone run down the syntax for me on
that? And also, I'm still not sure I know exactly how os.walk() works.
And, finally, the python docs all note that symbols like . and ..
don't work with these commands. How can I grab the directory that my
script is residing in?
>
Thanks.
>
>

'file' *is* the name of the file type, so one shouldn't reuse it as the
name of a variable as Dave did in his example.

the brackets are a "list comprehension" and they work like so:

files_with_ext = []
for filename in files:
if filename.endswi th(extension):
files_with_ext. append(filename )

The above is exactly equivalent to the [filename for filename in
files... ] form.

AFAIK, os.listdir('.') works fine, but you can also use
os.listdir(os.g etcwd()). However, both of those return the current
directory, which can be different than the directory your script's
residing in if you've called os.chdir() or if you start your script
from a different directory.
HTH.

(Also, if you're not already, be aware of os.path.isfile( ) and
os.path.isdir() . They should probably be helpful to you.)

Peace,
~Simon

[Steve M]

Re: newb question: file searching


jaysherby@gmail .com wrote:

I must ask, in the interest of learning, what is
>
[file for file in files if file.endswith(e xtension)]
>
actually doing? I know that 'file' is a type, but what's with the set
up and the brackets and all?

Other people explained the list comprehension, but you might be
confused about the unfortunate choice of 'file' as the name in this
example. 'file' is a built-in as you remarked. It is allowed, but a bad
idea, to use names that are the same as built-ins. Some people
characterize this as shadowing the built-in.

A similar, common case is when people use the name 'list' for a list
object. They shouldn't.

The example could have been written as:

[f for f in files if f.endswith(exte nsion)]

[jaysherby@gmail.com]

Re: newb question: file searching

Okay. This is almost solved. I just need to know how to have each
entry in my final list have the full path, not just the file name.
Also, I've noticed that files are being found within hidden
directories. I'd like to exclude hidden directories from the walk, or
at least not add anything within them. Any advice?

Here's what I've got so far:

def getFileList():
import os
imageList = []
for files in os.walk(os.getc wd(), topdown=True):
imageList += [file for file in files[2] if file.endswith(' jpg') or
file.endswith(' gif')]
return imageList