Python3 - Advice on a while loop with range? - python-3.x

Question

Good afternoon! I am relatively new to Python - and am working on an assignment for a class.
The goal of this code is to download a file, add a line of data to the file, then create a while loop that iterates through each line of data, and prints out the city name and the highest average temp from the data for that city.
My code is below - I have the output working, no problem. The only issue I am running into is an IndexError: list index out of range - at the end.
I have searched on StackOverflow - as well as digging into the range() function documentation online with Python. I think I just need to figure to the range() properly, and I'd be done with it.
If I take out the range, I get the same error - so I tried to change the for/in to - for city in mean_temps:
The result of that was that the output only showed 4 of the 7 cities - skipping every other city.
Any advice would be greatly appreciated!
here is my code - the screenshot link below shows output and the error as well:
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/world_temp_mean.csv -o mean_temp.txt
mean_temps = open('mean_temp.txt', 'a+')
mean_temps.write("Rio de Janeiro,Brazil,30.0,18.0")
mean_temps.seek(0)
headings = mean_temps.readline().split(',')
print(headings)
while mean_temps:
range(len(city_temp))
for city in mean_temps:
city_temp = mean_temps.readline().split(',')
print(headings[0].capitalize(),"of", city_temp[0],headings[2], "is", city_temp[2], "Celsius")
mean_temps.close()

Answer 1

You have used a while loop, when you actually want to use a for loop. You have no condition on your while loop, therefore, it will evaluate to True, and run forever. You should use a for loop in the pattern
for x in x:
do stuff
In your case, you will want to use
for x in range(len(city_temp)):
for city in means_temp:
EDIT:
If you have to use a while loop, you could have variable, x, that is incremented by the while loop. The while loop could run while x is less than range(len(city_temp)).
A basic example is
text = "hi"
counter = 0
while counter < 10:
print(text)
counter += 1
EDIT 2:
You also said that they expected you to get out of a while loop. If you want a while loop to run forever unless a condition is met later, you can use the break command to stop a while or for loop.

Answer 2

I've been stuck with this as well with the index error. My original code was:
city_temp = mean_temp.readline().strip(" \n").split(",")
while city_temp:
print("City of",city_temp[0],headings[2],city_temp[2],"Celcius")
city_temp = mean_temp.readline().split(",")
So I read the line then, in the loop, print the line, create the list from reading the line and if the list is empty, or false, break. Problem is I was getting the same error as yourself and this is because city_temp is still true after reading the last line. If you add..
print(city_temp)
to your code you will see that city_temp returns as "" and even though it's an empty string the list has content so will return true. My best guess (and it is a guess) it looks for the split condition and returns back nothing which then populates the list as an empty string.
The solution I found was to readline into a string first (or at the end of the whole loop) before creating the list:
city_temp = mean_temp.readline()
while city_temp:
city_temp = city_temp.split(',')
print(headings[0].capitalize(),"of",city_temp[0],headings[2],"is",city_temp[2],"Celcius")
city_temp = mean_temp.readline()
This time city_temp is checked by the while loop as a string and now returns false. Hope this helps from someone else who struggled with this