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May 26th, 2009

Optimizing this code

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First let me say thanks to everyone who has been responding to my posts and providing valuable insight. I have been trying to add rep whenever possible, and appreciate your help.

My assignment was to write a python code which takes data from an infile, then has the user specify a column out of the infile, and then the program writes only the information from that column to an outfile. Thanks to help from you guys, I've also been able to include a portion of the code which will skip over blank lines instead of crashing. I'd like to optimize/change the code with your suggestions. I feel that I've probably included too many operations and am being redundant in places. Here is my code, with comments which try to convey my level of understanding. Please add suggestions and point out where my comments are fallacious.

Python Syntax (Toggle Plain Text)
def columns(infile, outfile):
	f = open(infile,'r')
	o = open(outfile,'w')
 
	col = int(raw_input('Please select a column (starting at 0) from you in file, %s:' % (infile))) 
 
	temp = []   #Store an empty list
 
	for line in f:
		if not line.strip():   #If empty line, strip the new line character and remaining space 
			continue
		else:
			line = line.split() #Split lines so that they can be operated on via list operations
        		temp.append(line[col])	 #Write the user-specified column into the empty list, "temp
 
	o.write('\n'.join(temp))   
 
 
	print "See %s" % (outfile)  
 
	f.close()
	o.close()
def columns(infile, outfile):
	f = open(infile,'r')
	o = open(outfile,'w')

	col = int(raw_input('Please select a column (starting at 0) from you in file, %s:' % (infile))) 

	temp = []   #Store an empty list
 
	for line in f:
		if not line.strip():   #If empty line, strip the new line character and remaining space 
			continue
		else:
			line = line.split() #Split lines so that they can be operated on via list operations
        		temp.append(line[col])	 #Write the user-specified column into the empty list, "temp
		       
	o.write('\n'.join(temp))   
					

	print "See %s" % (outfile)  
	
	f.close()
	o.close()

Last edited by shoemoodoshaloo; May 26th, 2009 at 11:23 am.

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shoemoodoshaloo

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May 26th, 2009

Re: Optimizing this code

this isnt that big of a deal, but you could add col -= 1 after this:

Python Syntax (Toggle Plain Text)
	col = int(raw_input('Please select a column (starting at 0) from you in file, %s:' % (infile)))
	col = int(raw_input('Please select a column (starting at 0) from you in file, %s:' % (infile)))

this way, you can eliminate the "starting at 0" part and they will enter "1" for the first column.

Last edited by billymcguffin; May 26th, 2009 at 11:28 am.

billymcguffin

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May 26th, 2009

Re: Optimizing this code

Cool suggestion, added.

shoemoodoshaloo

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May 26th, 2009

Re: Optimizing this code

sure

billymcguffin

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May 26th, 2009

Re: Optimizing this code

Some of your comments may be overkill. Here's how I'd revise your function:

* Added Billy's suggestion from above
* I like comments on separate lines unless they're extremely short
* Tabs are an absolute no-no in my book
* No need to say if something: continue ... when there's no other action in the loop, simply omit the check for something

python Syntax (Toggle Plain Text)
def columns(infile, outfile):
    f = open(infile,'r')
    o = open(outfile,'w')
 
    col = raw_input('Please select a column from your input file, %s:' % (infile))
    col = int(col) - 1
 
    temp = []
    for line in f:
        line = line.strip()
        if line:
            # Split each line into columns
            line = line.split()
            # Write contents of user-specified columns to temp
            temp.append(line[col])
    o.write('\n'.join(temp))   
 
 
    print "See %s" % (outfile)  
    f.close()
    o.close()
def columns(infile, outfile):
    f = open(infile,'r')
    o = open(outfile,'w')

    col = raw_input('Please select a column from your input file, %s:' % (infile))
    col = int(col) - 1

    temp = []
    for line in f:
        line = line.strip()
        if line:
            # Split each line into columns
            line = line.split()
            # Write contents of user-specified columns to temp
            temp.append(line[col])
    o.write('\n'.join(temp))   
                    

    print "See %s" % (outfile)  
    f.close()
    o.close()

jlm699

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May 27th, 2009

Re: Optimizing this code

You unnecessary use the list.

python Syntax (Toggle Plain Text)
 
def columns(infile, outfile):
    f = open(infile,'r')
    o = open(outfile,'w')
 
    col = raw_input('Please select a column from your input file, %s:' % (infile))
    col = int(col) - 1
    for line in f:
        line = line.strip()
        if line:
            # Split each line into columns
            line = line.split()
            # Write contents of user-specified columns to temp
            o.write(line[col])
            o.write("\n")
    f.close()
    o.close() # this is the actual flushing
    print "See %s" % (outfile)
 
def columns(infile, outfile):
    f = open(infile,'r')
    o = open(outfile,'w')

    col = raw_input('Please select a column from your input file, %s:' % (infile))
    col = int(col) - 1
    for line in f:
        line = line.strip()
        if line:
            # Split each line into columns
            line = line.split()
            # Write contents of user-specified columns to temp
            o.write(line[col])
            o.write("\n")
    f.close()
    o.close() # this is the actual flushing
    print "See %s" % (outfile)

slate

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May 28th, 2009

Re: Optimizing this code

If you're really looking to get fancy use some list comprehension:

python Syntax (Toggle Plain Text)
 
def columns(infile, outfile):
    f = open(infile,'r')
    o = open(outfile,'w')
    #
    col = raw_input('Please select a column from your input file, %s:' % (infile))
    col = int(col) - 1
    o.write('\n'.join([line.strip().split()[col] for line in f if line != '\n']))
    #
    f.close()
    o.close() # this is the actual flushing
    print "See %s" % (outfile)
 
def columns(infile, outfile):
    f = open(infile,'r')
    o = open(outfile,'w')
    #
    col = raw_input('Please select a column from your input file, %s:' % (infile))
    col = int(col) - 1
    o.write('\n'.join([line.strip().split()[col] for line in f if line != '\n']))
    #
    f.close()
    o.close() # this is the actual flushing
    print "See %s" % (outfile)

Last edited by jlm699; May 28th, 2009 at 9:57 am.

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