[Tutor] text file help

[Alan Gauld]

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On 19/02/15 11:17, Tihomir Zjajic wrote:
> formular doznake.txt
>> red_broj = 1
>> vrs_drv = 21
>> prs_prec = 20
>> teh_kl = 2
>> red_broj = 2
>> vrs_drv = 21
>> prs_prec = 40
>> teh_kl = 3
>
> I assume red_broj indicates the start of a new record?
> So you can read three lines from the file after you
> find a red_broj entry?
>
> Something like this? (untested)
>
> kl_numbers = []
> with open('doznake.txt') as doznake
>     for line in doznake:
>        if line.startswith('red_broj')
>           num = makeNumber(next(doznake),next(doznake),next(doznake))
>           kl_numbers.append(num)
>
> def makeNumber(l1,l2,l3):
>     nums = []
>     for line in (s1,s2,s3):
>         nums.append(line.rstrip().split()[-1])
>     return ''.join(nums)
 > def makeNumber(l1, l2, l3):
 >    nums = []
 >    for lines in (s1, s2, s3):
 >        nums.append(line.rstrip().split() [-1])
 >    return ".join(nums) "
 >
 > kl_number = []
 > open("formular_doznake.txt")

You need to either assign the open result to a variable or use
the 'with' style (as in my example above).

 > for line in "formular_doznake.txt":
 >      line startswith("red_broj")

startswith is a method of string so you need a dot between line and 
startswith

 >     num = makeNumber(next("formular_doznake"), 
next("formular_doznake"), next("formular_doznake"))

next takes an iterator as an argument not a file name. This needs to
be the alias from the with statement or the variable you assign if using 
open.
example:

 >>> myfile = open("formular_doznake.txt")
 >>> print(next(myfile))

 >    kl_number.append(num)
 >
 > lpthw> python answer2.py formular_doznake.txt
 >   File "answer2.py" line 13
 > kl_number.append(num)
 > SyntaxError: invalid sintax

You should copy and paste the code and errors not re-type them.
its easier and more reliable.

BTW If using the open styule above you should close the file
at the end:

myfile.close()

One of the advantages of the with... style is that it auto-closes
the file for you.

-- 
Alan G
Author of the Learn to Program web site
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