How the answer is 6 ?

Question

def func(x):
res = 0
for i in range(x):
res += i
return res

print(func(4))

Answer 1

for i in range(4)
//this loop will run for i=0,1,2,3
res +=i
//res +=(0+1+2+3) = 6

//try this code
def func(x):
res = 0
for i in range(x):
res+=i

print (res)
return res

print(func(4))

Answer 2

Your not adding 1 each time. you are adding the iteration.

0+1+2+3=6