CODEWITHSUNDEEP
pythonlistindexing
Renves
Renves

Reputation: 11

list index out of range (with while loop)

I'm working on an a assignment for an edx course and I'm having an "index out of range" error in my code when it runs a while loop, even though it gives the right output eventually.

This is my code:

# [] create The Weather
# [] copy and paste in edX assignment page
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/world_temp_mean.csv -o mean_temp.txt

mean_temp = open('mean_temp.txt', 'a+')
mean_temp.write("Rio de Janeiro,Brazil,30.0,18.0\n")

mean_temp.seek(0)

headings = mean_temp.readline().split(',')

city_temp = mean_temp.readline().split(',')
while city_temp:
    print(headings[0].capitalize(), "of", city_temp[0], headings[2], "is", city_temp[2], "Celsius")
    city_temp = mean_temp.readline().split(',')

mean_temp.close()

Upvotes: 1

Views: 143

Answers (2)

tobias_k
tobias_k

Reputation: 82899

When you hit the empty last line, i.e. '', the result of mean_temp.readline().split(',') is [''], not [], hence your loop continues and you get the index error. You could check the len instead:

while len(city_temp) == 4:
    print(headings[0].capitalize(), "of", city_temp[0], headings[2], "is", city_temp[2], "Celsius")
    city_temp = mean_temp.readline().split(',')

However, the better way to handle this would be with a proper for loop and csv reader:

import csv
with open('mean_temp.txt') as f:
    reader = csv.reader(f)
    header = next(reader)
    for city in reader:
        print(header[0].capitalize(), "of", city[0], header[2], "is", city[2], "Celsius")

(The file format would work even better with a DictReader, but the way you print that line doesn't.)

Upvotes: 0

peter554
peter554

Reputation: 1378

I've tested this and it should work. I think your while clause isn't correctly finding the end of the file - a for loop works and is cleaner.

with open("mean_temp.txt", "a") as f:
    f.write("\nRio de Janeiro,Brazil,30.0,18.0")

with open("mean_temp.txt", "r") as f:
    headings = f.readline().split(',')
    for next_line in f:
        next_line = next_line.split(',')
        print(headings[0].capitalize(), "of", next_line[0], headings[2], "is", next_line[2], "Celsius")

Upvotes: 1

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