Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

Python function to handle multiple file input types for an argument

Posted on 2011-03-21
9
Medium Priority
?
546 Views
Last Modified: 2012-05-11
I previously posted http://www.experts-exchange.com/Programming/Languages/Scripting/Python/Q_26881841.html but I would now like to take a file, folder or wildcards via command line using a single option/arg. How can the same be achieved using a function? Thanks
0
Comment
Question by:adamshields
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 4
9 Comments
 
LVL 29

Expert Comment

by:pepr
ID: 35183716
If I understand you well, then you want to get a single argument, and depending on whether it is a directory, a file, or a mask, you want to have a function that returns filenames from the directory, the file, or the files got by expanding the mask.  Is that what you want?

If yes, I suggest to create a generator function that produces the filenames independently on what you pass.  Or it could be no file, or the single file, or the files got via expanded mask, or the files from inside the directory.  (I know I am repeating the same using the other words.)

Then if you get the argument myArg, the you will use it this way:

for fname in myFiles(myArg):
     process(fname)

Open in new window


Do you want something like this?
0
 
LVL 3

Author Comment

by:adamshields
ID: 35183757
@pepr: how would this work with my current logic? I am only going to be using the options.filename and doing away with the options.directory argument.

    filenames_or_wildcards = []

# remove next line if you do not want allow to run the script without the -f -d
# option, but with arguments
    filenames_or_wildcards = args # take all filenames passed in the command line

# if -f was specified add them (in current working directory)
    if options.filename is not None:
        filenames_or_wildcards.append(options.filename)

# if -d was specified or nothing at all add files from dir
    if options.directory is not None:
        filenames_or_wildcards.append( os.path.join(options.directory, "*") )

# Now expand all wildcards
# glob.glob transforms a filename or a wildcard in a list of all matches
# a non existing filename will be 'dropped'
    all_files = []
    for filename_or_wildcard in filenames_or_wildcards:
        all_files.extend( glob.glob(filename_or_wildcard) )

Open in new window

0
 
LVL 29

Accepted Solution

by:
pepr earned 2000 total points
ID: 35184026
If yes, try the following code (test data and the script attached in the zip):

a.py
import glob
import os
import sys


def myFiles(arg):
    '''A generator function that diggs all files from the argument.'''
    
    if os.path.isfile(arg):                 # for a single file, return the file
        yield arg
        
    elif os.path.isdir(arg):                # for a directory, return all files
        for item in os.listdir(arg):        # produces bare names
            fname = os.path.join(arg, item) # path + bare name
            if os.path.isfile(fname):       # only the files are returned
                yield fname  # no normalization of slashes/backslashes here
    else:
        for fname in glob.glob(arg):        # it could be a mask -- expand it
            if os.path.isfile(fname):       # only the files are returned
                yield os.path.normpath(fname)  # normalize slashes/backslashes


myArg = ''
if len(sys.argv) > 1:
    myArg = sys.argv[1]
    
print 'For the explicitly given argument:', repr(myArg)
for fname in myFiles(myArg):
    print fname
    
# For other tests the returned filenames are printed as one list.    
print '-' * 70
arg = ''                   # empty argument
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir'            # existing directory
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'nodirDir'           # non-existing directory
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/a.txt'      # existing file
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/nofile.txt'  # non-existing file
print 'Test for', repr(arg)
print list(myFiles(arg))
    
print '-' * 70
arg = 'testDir/.'           # existing directory -- another form
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'noDir/*.txt'         # mask expanding to no file
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/*'           # all files from the existing directory
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/?.txt'       # one-letter + extension
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/a*.txt'      # a-prefixed filenames
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/*a.txt'      # a-suffixed filenames
print 'Test for', repr(arg)
print list(myFiles(arg))

Open in new window


For the directory like (Czech interface):

C:\tmp\_Python\adamshields\Q_26901398\testDir>ls -l
celkem 5
-rwx------+ 1 Petr None 10 Mar 21 20:18 a.txt
-rwx------+ 1 Petr None 11 Mar 21 20:18 aa.txt
drwx------+ 1 Petr None  0 Mar 21 20:35 ad
drwx------+ 1 Petr None  0 Mar 21 20:35 adir
-rwx------+ 1 Petr None 14 Mar 21 20:19 ax.txt
-rwx------+ 1 Petr None 14 Mar 21 20:19 ba.txt
drwx------+ 1 Petr None  0 Mar 21 20:35 subdir
-rwx------+ 1 Petr None 10 Mar 21 20:34 x.txt
drwx------+ 1 Petr None  0 Mar 21 20:35 z

Open in new window


It prints the following on my console:

c:\tmp\_Python\adamshields\Q_26901398>python a.py testdir/b*
For the explicitly given argument: 'testdir/b*'
testdir\ba.txt
----------------------------------------------------------------------
Test for ''
[]
----------------------------------------------------------------------
Test for 'testDir'
['testDir\\a.txt', 'testDir\\aa.txt', 'testDir\\ax.txt', 'testDir\\ba.txt', 'testDir\\x.txt']
----------------------------------------------------------------------
Test for 'nodirDir'
[]
----------------------------------------------------------------------
Test for 'testDir/a.txt'
['testDir/a.txt']
----------------------------------------------------------------------
Test for 'testDir/nofile.txt'
[]
----------------------------------------------------------------------
Test for 'testDir/.'
['testDir/.\\a.txt', 'testDir/.\\aa.txt', 'testDir/.\\ax.txt', 'testDir/.\\ba.txt', 'testDir/.\\x.txt']
----------------------------------------------------------------------
Test for 'noDir/*.txt'
[]
----------------------------------------------------------------------
Test for 'testDir/*'
['testDir\\a.txt', 'testDir\\aa.txt', 'testDir\\ax.txt', 'testDir\\ba.txt', 'testDir\\x.txt']
----------------------------------------------------------------------
Test for 'testDir/?.txt'
['testDir\\a.txt', 'testDir\\x.txt']
----------------------------------------------------------------------
Test for 'testDir/a*.txt'
['testDir\\a.txt', 'testDir\\aa.txt', 'testDir\\ax.txt']
----------------------------------------------------------------------
Test for 'testDir/*a.txt'
['testDir\\a.txt', 'testDir\\aa.txt', 'testDir\\ba.txt']

Open in new window


Feel free to ask on what you want to have explained. (Strange English here, righ?  My fault ;)
Q-26901398.zip
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 
LVL 29

Expert Comment

by:pepr
ID: 35184061
Well, I was typing meanwhile. The myFiles() processes a single argument but it can easily be adjusted to proces or a single argument or a list of arguments.  Any single argument could be a file, a dir, a mask.
0
 
LVL 3

Author Closing Comment

by:adamshields
ID: 35184080
Thanks for the quick response!
0
 
LVL 29

Expert Comment

by:pepr
ID: 35184178
Have a look at the modified function:

b.py
import glob
import os
import sys


def myFiles(arg):
    '''A generator function that diggs all files from the argument.'''
    
    if isinstance(arg, str):     # single string
        lst = [ arg ]            # convert to the list
    elif isinstance(arg, list):  # list is OK,
        lst = arg                # no conversion
    else:
        print 'Unexpected arg:', repr(arg)
        sys.exit(1)
    # Warning: the arg identifier reused here (not ideal).
    for arg in lst:
        if os.path.isfile(arg):                 # for a single file, return the file
            yield arg
            
        elif os.path.isdir(arg):                # for a directory, return all files
            for item in os.listdir(arg):        # produces bare names
                fname = os.path.join(arg, item) # path + bare name
                if os.path.isfile(fname):       # only the files are returned
                    yield fname  # no normalization of slashes/backslashes here
        else:
            for fname in glob.glob(arg):        # it could be a mask -- expand it
                if os.path.isfile(fname):       # only the files are returned
                    yield os.path.normpath(fname)  # normalize slashes/backslashes

print '-' * 70
arg = 'testDir/a.txt'      # existing file
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = 'testDir/.'           # existing directory -- another form
print 'Test for', repr(arg)
print list(myFiles(arg))

print '-' * 70
arg = ['noDir/*.txt',       # mask expanding to no file
       'testDir/*',         # all files from the existing directory
       'testDir/?.txt',     # one-letter + extension
       'testDir/a*.txt',    # a-prefixed filenames
       'testDir/*a.txt',    # a-suffixed filenames
      ]
print 'Test for', repr(arg)
print list(myFiles(arg))

Open in new window


It prints:
C:\tmp\_Python\adamshields\Q_26901398>python b.py
----------------------------------------------------------------------
Test for 'testDir/a.txt'
['testDir/a.txt']
----------------------------------------------------------------------
Test for 'testDir/.'
['testDir/.\\a.txt', 'testDir/.\\aa.txt', 'testDir/.\\ax.txt', 'testDir/.\\ba.txt', 'testDir/.\\x.txt']
----------------------------------------------------------------------
Test for ['noDir/*.txt', 'testDir/*', 'testDir/?.txt', 'testDir/a*.txt', 'testDir/*a.txt']
['testDir\\a.txt', 'testDir\\aa.txt', 'testDir\\ax.txt', 'testDir\\ba.txt', 
'testDir\\x.txt', 'testDir\\a.txt', 'testDir\\x.txt', 'testDir\\a.txt', 
'testDir\\aa.txt', 'testDir\\ax.txt', 'testDir\\a.txt', 'testDir\\aa.txt', 
'testDir\\ba.txt']

Open in new window


Notice that the names are not uniqued in the case.
0
 
LVL 3

Author Comment

by:adamshields
ID: 35184197
Great thanks, lastly, if I were using:

def main()

Where would def myFiles(arg): be located, before, after or in the main()?

Thanks
0
 
LVL 29

Expert Comment

by:pepr
ID: 35184230
It does not matter in Python.  But it may be good to keep conventions from other languages and put it earlier than main().

Actually, Python interprets the .py file from beginning to the end.  However, the first and the only interpretation means compilation.  Any def, class or such is converted to the internal object, any other command is interpreted.
0
 
LVL 3

Author Comment

by:adamshields
ID: 35184281
Okay thanks!
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article is meant to give a basic understanding of how to use R Sweave as a way to merge LaTeX and R code seamlessly into one presentable document.
When we want to run, execute or repeat a statement multiple times, a loop is necessary. This article covers the two types of loops in Python: the while loop and the for loop.
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
Suggested Courses

609 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question