Why interpreter accepts indentation made with spaces and not those by tabs

[sylas]

For the whole file I used tabs. I used vim. It did not run well.

sylvain@sylvain-HP-Laptop-15-bw0xx:~$ cat new2.py
#!/usr/bin/python3
#!/usr/bin/env python3
#new2.py

def silly(n, x):
    m=n
    stack = [iter(range(m))]
    total=0
    while stack:
        try:
            i = stack[-1].__next__()
        except StopIteration:
            stack.pop()
            continue
        total += i   
        if total >= x:
            break
        if i ==  5:
            m -= 1
            stack.append(iter(range(m)))
    return total


print(silly(1,2))


print(silly(0,1))
print(silly(2,3))
print(silly(3,4))
										
sylvain@sylvain-HP-Laptop-15-bw0xx:~$ 

The first is for try: Instead of tabs I use spaces. Error repaired. Next error is for the next line.nd
It is really amazing ! How interpreter finds you used tabs and not spaces ???