[Tutor] Multiple file open

[nitin chandra]

Hello All,



>> Please guide with the syntax.
>
> All beginners tutorials on the web teach the syntax of python.. I am
> unsure what your questions is.

My bad .... with code.

>
>> below is the existing program with Formula A (Mean). Formula B will be
>> Extrapolation,
>> also I have not been able to do justice to 'except IOError:' part.The
>
> It has many errors which need fixing but..
>
>> program ends with an error.
>
> And if you get an error always make sure you provide it to this list.
> People on this list can not read minds ;-).

I was wondering ... what else i need to post. Thank you. I REALLY need
to keep that in mind.

>
>> ********************************
>> import sys,os, fileinput
>>
>>
>> file11 = raw_input('Enter PR1 File name :')
>> fp1 = open(file11,'r')
>>
>> file12 = raw_input('Enter PR3 File Name :')
>> fp2 = open(file12,'r')
>>
>> file3 = raw_input('Enter PR2 / PR4 OUTPUT File Name :')
>> fp3 = open(file3,'w')
>
> What happens when you enter a wrong filename? It will raise IOError
> the moment you use open(). Below is 1 example of what you might want
> tot do.
>
> file11 = raw_input('Enter PR1 File name :')
> try:
>    fp1 = open(ffile11, 'r')
> except IOError:
>   sys.exit('Could not open file: %s' % file11)
>

Adding this 'try-except'


>> while True:
>>   try:
>>       line1A = fp1.readline()
>
> You can read and split the line in 1 go.
>         line1 = fp1.readline().split(",")

:) so much better ... adding again.

>
>>       line1B = fp2.readline()
>>       line1 = line1A.split(",")
>
> You can now remove the above, see earlier comment.
>
>>       col1 = line1[0]
>>       col2 = line1[1]
>>       col3 = line1[2]
>>       col4 = line1[3]
>>       col5 = line1[20]
>>       col6 = line1[21]
>>       col7 = line1[22]
>>       line2 = line1B.split(",")
>>       col8 = line2[1]
>>       col9 = line2[2]
>>       col10 = line2[3]
>>       col11 = line2[20]
>>       col12 = line2[21]
>>       col13 = line2[22]
>
> Above you create a list "line1 = fp1.readline().split(",")". Lists are
> mutable so you can add, remove and insert new items. You can also
> access the items in the list by index. You can even add 2 lists to
> make a new list, eg: .
>
>>>> [1,2,3,4,5] + [6,7,8,9,0]
> [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
>
> Now try and apply this to all your col<num> variables.

Actually I needed to do further computation, therefore I preferred to
keep the values separate.

>
>>       # calculation of PR2 as per formula
>>       #(A+B)/2 , ie. Mean of the two values
>>       col14 = ( (float(col2)) + (float(col8)) / 2)
>
> You can write this as:
>  col14 = (float(line1[1])) + (float(line2[1])) / 2)

I did this in one of my attempts. Pl dont ask me what was the error.
Did not save.

>
> And avoid creating all these col variables. But what would happen if
> col2/line1[1] has a value of "I am not a number"? Do note the comment
> below on the actual calculation.

I am keeping (cleaning) the Input data file as per the program.

>
>>       col15 = ( (float(col3)) + (float(col9)) / 2)
> <snipped some more>
>>       col19 = ( (float(col7)) + (float(col13)) / 2)
>
> Your "mean" calculation is wrong (hint, division has precedence over adding).

THANKS .... aarrhh ... I missed another pair of braces.


>
> Greets
> Sander
>

Once the Final version is over will post it.

Thanks

Nitin