What does << do in Python? -


i solved problem on project euler took 4 minutes run, above recommended time, looking through different solutions in forum. 1 of them included symbol << in list comprehension. looked like

blist.extend([(i << 1) + 3 in range(num) if alist.get(i)])

i can't find anywhere << symbol does. can me?

it's bit shift operator (python docs), , common among many programming languages, such c, java, php, etc. according python docs:

they shift first argument left or right number of bits given second argument.

a right shift n bits defined division pow(2, n). left shift n bits defined multiplication pow(2, n). negative shift counts raise valueerror exception.

so in specific case, i << 1 means left shift 1 bit, equivalent multiplying 2^1, or 2.


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