What is equivalent to
for (I=2; I<n; I*=2)
in python. I tried to do this with range() function and I know how it works with increment only. But here I want to multiply it in each iteration. I don't want to do it manually in side the loop
2 Answers
While while is easy, while is also slow. Try:
In [3]: import math
In [4]: n = 10
In [5]: for i in (2**n for n in range(1, int(math.log2(n)) + 1)):
...: print(i)
...:
2
4
8
In [6]: n = 40
In [7]: for i in (2**n for n in range(1, int(math.log2(n)) + 1)):
...: print(i)
...:
2
4
8
16
32
In [8]: n = 60
In [9]: for i in (2**n for n in range(1, int(math.log2(n)) + 1)):
...: print(i)
...:
2
4
8
16
32
In [10]: n = 100
In [11]: for i in (2**n for n in range(1, int(math.log2(n)) + 1)):
...: print(i)
...:
2
4
8
16
32
64
answered Nov 21, 2016 at 17:35
juanpa.arrivillaga
97.7k14 gold badges141 silver badges190 bronze badges
3 Comments
quantummind
please consider, that 1/2 = 0 in python2, so 0.5 can be more general; plus n**(0.5) is not what you need here. You should use log2.
juanpa.arrivillaga
@quantummind again, you are absolutely correct. I've edited it one more time. It's been one of those mornings...
Kevin_Kinsey
>>> import this ;)
Simple is the rule in python. While is easy:
n = 20
i = 2
while (i<n):
print "the i variable is "+str(i)
i = i * 2
I (originally, this has since been changed) used addition for this simple example, multiplication would simply use the "*" operator as you did.
3 Comments
quantummind
The question says I*=2, which is multiplication, i = i + 2 in your answer is addition.
Kevin_Kinsey
The comment notes that. Concept is being taught; I write real code for money.
quantummind
OK, I would like to revoke down-vote, but I cannot do that until you edit your answer. Consider that you might do what the customer asked, instead of writing what you want, and tell him that he can modify it to work as he/she wanted. :-)
0 * 2is0.