a question about "for loop" and "range" function.

Question

#for this code,why the output is 10 rather than 20？
x=0
for i in range(5):
for j in range(i):
x+=j
print(x)
"""
I thought the output should be 0+(0+1)+(0+1+2)+(0+1+2+3)+(1+2+3+4)=20, but the real output is 10,why?I get confused.
"""

Answer 1

Iterations:
1. 0to0 = no increase
2. 0to1 = +0
3. 0to2 = +0+1
4. 0to3 = +0+1+2
5. 0to4 = +0+1+2+3

Sum: 10

Answer 2

@James
Long explainations can be really good, you are right there.
I always try to explain it long too.
But this one was a bit tricky, even for me.
Sometimes you have to keep things simple🛀

Answer 3

trying to replicate the code:

i = 0 --> x = 0
i = 1 --> x = 0 + 0 = 0
i = 2 --> x = 0 + 0 + 1 = 1
i = 3 --> x = 1 + 0 + 1 + 2 = 4
i = 4 --> x = 4 + 0 + 1 + 2 + 3 = 10