Python ( iteration problem ) with an exercice

Question

The code :

import pandas as pd 
import numpy as np
import csv
data = pd.read_csv("/content/NYC_temperature.csv", header=None,names = ['temperatures'])

np.cumsum(data['temperatures'])
printcounter = 0
list_30 = [15.22]#first temperature , i could have also added it by doing : list_30.append(i)[0] since it's every 30 values but doesn't append the first one :)
list_2 = [] #this is for the values of the subtraction (for the second iteration)
for i in data['temperatures']: 
    if (printcounter == 30):
        list_30.append(i)
        printcounter = 0
    printcounter += 1
**for x in list_30:
  substract = list_30[x] - list_30[x+1]**
  list_2.append(substraction)
print(max(list_2))

Hey guys ! i'm really having trouble with the black part.

**for x in list_30:
  substract = list_30[x] - list_30[x+1]**

I'm trying to iterate over the elements and sub stracting element x with the next element (x+1) but the following error pops out TypeError: 'float' object is not iterable. I have also tried to iterate using x instead of list_30[x] but then when I use next(x) I have another error.

question from:https://stackoverflow.com/questions/65940253/python-iteration-problem-with-an-exercice

Answer 1

for x in list_30: will iterate on list_30, and affect to x, the value of the item in the list, not the index in the list.

for your case you would prefer to loop on your list with indexes:

index = 0
while index < len(list_30):
  substract = list_30[index] - list_30[index + 1]

edit: you will still have a problem when you will reach the last element of list_30 as there will be no element of list_30[laste_index + 1], so you should probably stop before the end with while index < len(list_30) -1:

in case you want the index and the value, you can do:

for i, v in enumerate(list_30):
  substract = v - list_30[i + 1]

but the first one look cleaner i my opinion