I am not able to understand this anomaly in Python

Question

If try to change an element inside a globally declared array I get the desired result in this code:

a = [['a','b','c'], ['d','e','f'], ['g','h','i']]
for r in a:
 for c in r:
 print(c,end = " ")
 print()
print()
def changeValue(ch):
 a[0][0]=ch
ch=input("Please enter a character\n")
changeValue(ch)
for r in a:
 for c in r:
 print(c,end = " ")
 print()
print()

But in the following code, I don't get the desired result ,i.e, the element at a[0][0] doesn't change

a = [['a','b','c'], ['d','e','f'], ['g','h','i']]
for r in a:
 for c in r:
 print(c,end = " ")
 print()
print()
def enterSymbol(pos,ch):
 if pos==1:
 a[0][0]=ch
 elif pos==2:
 a[0][1]=ch
pos=input("Enter a position\n")
enterSymbol(pos,'X')
for r in a:
 for c in r:
 print(c,end = " ")
 print()

Please help

• Klaus D.: Your pos is a string and can not be equal to a number.

Answer 1

The pos in input is always a string. That is why it will not go into the if conditions in enterSymbol (string compared to int).

pos = int(input("Enter a position"))

Replace this with the pos and it should work

Answer 2

The input function returns a string, not a number:

>>> pos=input("Enter a position\n")
Enter a position
1
>>> pos
'1'
>>> 

So this condition:

if pos==1:

is never True.

One way to solve your problem is to change your code to:

pos=int(input("Enter a position\n"))

Answer 3

Python understands your entry input as a char, not an integer. You can for example replace your if pos==1: with if pos=='1': and that will work.