How do I loop through certain parts of a text file in Python?

Question

Currently, a Python beginner looking for some help. I'm reading from a text file with 365 lines of integers. Each integer is representative of a day of the year. Like this, but for 365 lines:

I need to go through the whole file and separate the 365 days into each of the 12 months and take the average of the numbers of each month. For instance, the first 31 lines are January, take the average, print it, then continue from there...

At this point I have written code that goes through the whole file and gives a total for the year and an average per day, but am stuck on splitting the file into the separate months and taking individual averages. What do I do to achieve this?

Here's my current code:

import math

def stepCounter ():
    stepsFile = open("steps.txt", "r")
    stepsFile.readline()

    count = 0
    for line in stepsFile:
        steps = int(line)
        count = count + steps
        avg = count / 365
    print(count, "steps taken this year!")
    print("That's about", round(avg), "steps each day!")

  stepsFile.close()

stepCounter()

I hope this question was clear enough. Thanks for any help!

Since it is ordered and you know how many days each month has, maybe count the lines you have read to know in which month you are? First 31 are january etc. — voiDnyx
– voiDnyx, Commented Oct 26, 2017 at 21:06

Ilja Everilä · Accepted Answer · 2017-10-26 21:30:02Z

You'll have to have the number of days per month. Either use a fixed table, or you could ask the calendar module:

In [11]: months = [calendar.monthrange(2017, m)[1] for m in range(1, 13)]

In [12]: months
Out[12]: [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

In case you decide to use a fixed table the only month of interest is February during leap years. You could just increment that if calendar.isleap() is True.

Given an open file of integer per row you could simply slice it suitably, map int() over the slices, and use statistics.mean():

In [17]: from statistics import mean

In [18]: from itertools import islice

In [19]: [mean(map(int, islice(the_file, mdays))) for mdays in months]
Out[19]: [15, 44.5, 74, 104.5, 135, 165.5, 196, 227, 257.5, 288, 318.5, 349]

where the_file was simply

In [13]: from io import StringIO

In [14]: the_file = StringIO()

In [15]: the_file.writelines(map('{}\n'.format, range(365)))

In [16]: the_file.seek(0)
Out[16]: 0

Prune · Accepted Answer · 2017-10-26 21:17:29Z

0

First, you need a list with the quantity of days in each month:

month_len = [31, 28, 31,
             30, 31, 30,
             31, 31, 30,
             31, 30, 31]

Now write a loop to step through the months, with another inside to step through the days:

for month_num in range(12):
    # Start a new month

    for day_num in range(month_len[month_num]):
        #Process one day

Do remember that Python indexing starts at 0, so you'll have month_num running 0-11, and day_num running 0-30 at most.

Can you take it from there?

RESPONSE TO OP'S COMMENT

Okay, you're handicapped: lists are disallowed. Instead, try this:

for month_num in range(1, 12):
    month_len = 31
    if month_num = 2:
        month_len = 28
    elif month_num = 4 or
         month_num = 6 or
         month_num = 9 or
         month_num = 11:
        month_len = 30

    for day_num in range(month_len):

edited Oct 26, 2017 at 21:17

answered Oct 26, 2017 at 21:06

Prune

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2 Comments

Tim Ludwig Over a year ago

As embarrassing as this is, we haven't even covered lists yet. Is there a way to do it by declaring months as constants?

Prune Over a year ago

Then how do you iterate through those constants? In this case, I suggest some ugly if statements. See edited answer.

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