Question

http://ideone.com/QaVoJ this was one of my solutions to the hw1 in udacity robotics class. Why is it giving a veeeery slightly different answer to the question, compared to the standard solution?

Answer 1

i can't understand anything in ur code where you use bazillion commands in one square brackets lol

and why you use xrange?

Answer 2

that's mine code http://ideone.com/SoZU3
but it's probably written in not pythonic way :D

Answer 3

xrange is better than range if I'm just going to use the numbers; xrange is a generator that just yields numbers if you call it (requires less memory than an entire list), whereas range returns a list (requiring memory to store a whole list)

Answer 4

what happens if i type a=xrange(5)?

Answer 5

then a will be equal to a generator object 'xrange(5)'

Answer 6

http://ideone.com/XhYt1

Answer 7

so better always use xrange in for loop and use range only if you want to create list and assign it to some variable?

Answer 8

right

Answer 9

almost 2 times faster with 100millions

>>> timeit.Timer('for i in xrange(100000000):pass').timeit(1)
2.7219030857086182
>>> timeit.Timer('for i in range(100000000):pass').timeit(1)
5.6206169128417969

but when i try to do with 1 billion
>>> timeit.Timer('for i in xrange(1000000000):pass').timeit(1)
27.099134922027588
>>> timeit.Timer('for i in range(1000000000):pass').timeit(1)
MemoryError

Answer 10

lol... did the python list of 1 billion integers kill your system?

Answer 11

not kill just memory error :D
does it allow you to create such list?

Answer 12

My system only has 1GB of memory :(

Answer 13

why this doesn't work?

a=[]
timeit.Timer("for i in xrange(1000000000):a.append('')").timeit(1)
gives NameError: global name 'a' is not defined

timeit.Timer("a=[];for i in xrange(1000000000):a.append('')").timeit(1)
gives SyntaxError: invalid syntax

Answer 14

in a.append its double single '

Answer 15

try defining a function, and then timing that. will it still give errors? never used timeit myself :(

Answer 16

can you make void function? what my function should return? or just anything

Answer 17

If you don't have a `return' keyword anywhere in the function, or if you use `return' alone (without an expression), then the function returns `None'

Answer 18

NameError: global name 'testbillion' is not defined

Answer 19

after 5minutes and 12 second got memory error, but my RAM usage didn't increase at all looking at system monitor

Answer 20

however it created list of this length
>>> len(a)
496880822