CODEWITHSUNDEEP
pythonparsing
MBasith
MBasith

Reputation: 1499

Python subtraction in for loop

I am in need of some help doing some simple calculations in a for loop. I have two columns in the below example file. Column 1 is the date-time-hr-min-ss and column 2 is a value. I would like to print through the file and calculate the difference between the current value and the value of the previous hour. I attempted the code below but not able to subtract the previous hour value. Can I get some help/direction in correcting my code below? Thanks in advance.

File Contents:

20160823220000 1208091708
20160823230000 1209559863
20160824000000 1210706089
20160824010000 1211612458
20160824020000 1212410614
20160824030000 1213059346

My Code:

with open('datecount.txt') as data:
    z = 0
    for line in data:
        x = (line.strip().split())
        num = int(x[1])
        z = num
        print(z - z)

Desired Output:

date-time-hr-min-ss Value       Delta-from-prev-Hr
==========================================================
20160823220000      1208091708  N/A 
20160823230000      1209559863  1468155 
20160824000000      1210706089  1146226
20160824010000      1211612458  906369
20160824020000      1212410614  798156
20160824030000      1213059346  648732

Upvotes: 0

Views: 2898

Answers (2)

Luke
Luke

Reputation: 848

Well if you can assume that each consecutive line in your file will be the hour following the previous hour, you don't need to even worry about messing with the time column. Just use this..

with open('datecount.txt') as data:
    z = 0
    for line in data:
        x = (line.strip().split())
        num = int(x[1])
        print(num - z)
        z = num

Your code was pretty much doing this already, you just needed to print (num - z) before assigning z to num. And also you had print(z-z) not print(num - z)

Upvotes: 1

karlosss
karlosss

Reputation: 3155

with open('datecount.txt') as data:
    prev = 0
    for line in data:
        value = int(line.strip().split()[1])
        print(value - prev)
        prev = value

It is a good idea to name the variables so that their names make sense. In other words, leave x, y, z in maths.

Upvotes: 3

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