[Tutor] A list in list problem

[János Juhász]

Hi Dave,

> From: dave s <pythontut at pusspaws.net>
> Subject: [Tutor] A list in list problem
> To: python tutor <tutor at python.org>
> Message-ID: <200608210959.01834.pythontut at pusspaws.net>
> Content-Type: text/plain;  charset="us-ascii"

> def CSV_Lines(self, csv, from_, to):
> """Returns a list of cleaned up lines from csv 'from_' line
> number  'to' line number"""

>        clean_line = clean_csv = []
>        for string in range(from_, to):
>               split_string = csv[string].split(',')
>               split_string = split_string[1:-1]  # Strip the LHS column 
+ the /n'
>               if split_string[0] == '' : continue  # Skip empty lines
>               print '##########################'
>               print 'split_string ', split_string
>               for string in split_string:
>                       if len(string) > 0: 
clean_line.append(string[1:-1])
>               print 'clean_line ',clean_line
>               clean_csv.append(clean_line)
>               print 'clean_csv ',clean_csv
>               clean_line = []
> 
> But I get clean_csv trouble  ...

> ubuntu at ubuntu:~/python_develop/unison/PxQxAudit/main$ ./crosscheck.py
> ##########################
> split_string  ['"temp1"', '"wow a variable"', '', '', '']
> clean_line  ['temp1', 'wow a variable']
> clean_csv  ['temp1', 'wow a variable', [...]]
> ##########################
> split_string  ['"temp2"', '', '', '', '']
> clean_line  ['temp2']
> clean_csv  ['temp1', 'wow a variable', [...], ['temp2']]
> ubuntu at ubuntu:~/python_develop/unison/PxQxAudit/main$

> ie clean_csv ends up as ['temp1', 'wow a variable', [...], ['temp2']] 
instead
> of [[temp1, wow a variable], [temp2]]


You have used string as variable name two times, once as an integer and 
once as a field in the line.
It should be avoided.

I like list comprehension in this case.

def CSV_Lines2(csv, from_, to):
    csv = csv[from_ : to]                                       # We are 
interested just here
    csv = [line.split(',') for line in csv]     # Make a 2D array from the 
list
    return [LineItems[1:-1] for LineItems in csv if len(LineItems) > 2] 
                    # filter out first and last columns, and lines with 
too less items



csv = """Header1
Header2
temp1,12,20,1
temp2,22,22,2
temp3,33,44,3
temp4,34,64,4
Footer1
Footer2"""

csv = csv.split('\n')
print CSV_Lines2(csv, 2, 6)
>>>[['12', '20'], ['22', '22'], ['33', '44'], ['34', '64']]


Yours sincerely, 
______________________________
Janos Juhasz 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.python.org/pipermail/tutor/attachments/20060821/bf941136/attachment.htm