Python if/or statement confusion [duplicate]

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• How do I test one variable against multiple values? 16 answers

I'm very new to coding of any kind and there's something that I'm struggling to understand. I'll break it all down below...

The problem: Find all integers between 1 and 1000 that contain the digits 6 or 7 in them.

My first attempt:

for i in range(1000):
if ('6' or '7') in str(i):
    print(i)

My final solution:

for i in range(1000): if '6' in str(i) or '7' in str(i): print(i)

The final solution works fine but I don't understand why my original code doesn't work. When using the original, only the first digit (6) would be printed. Moreover, if I leave the parentheses out of the original then range(1000) is printed in its entirety which has confused me further. Any help would be greatly appreciated!