I was trying to write a complex list comprehension but I am not sure how I am supposed to do it. I have the following for loop which I am trying to turn into a list comprehension
number = 10
deci_list = []
for i in sorted(list(range(9)), reverse=True):
if 2**i <= number:
deci_list.append(1)
number -= 2**i
else:
deci_list.append(0)
I was struggling to turn this into a list comprehension and this is what I have so far:
thing = sorted(list(range(9)), reverse=True)
new_thing = ['1' if 2**i <= number number -= 2**i else '0' for i in thing]
however, I do not know how to add the line number -= 2**i because it gives me an error every time I try to add it
new_thing = ['1' if 2**i <= number number -= 2**i else '0' for i in t
hing]
^^^^^^^^^^^^^^^^^^^^^
SyntaxError: expected 'else' after 'if' expression
You're getting a syntax error due to the assignment, =, operator. It isn't supposed to be used in a list comprehension. Here's one way to work around the situation. Note that sorted(list(range(9)), reverse=True) could be replaced with range(8, -1, -1).
number = 10
def operator(index):
global number
if 2 ** index <= number:
number -= 2 ** index
return 1
else:
return 0
print([operator(index) for index in range(8, -1, -1)]) # Or: list(map(operator, range(8, -1, -1)))
Edit: As suggested by @ShadowRanger in the comment section, it is generally not a good idea to play with global variables in a function as it couples the two [essentially requiring you to reset the global variable or do something similar when you want to reuse the function]. You could wrap the two in a class to make it reusable.
However, I would recommend list comprehensions only at places where they do not compromise on readability. What you have in the original snippet is completely alright.