What is the reason for having in Python

Question

I saw this in someone s code  y   img index    num images  where img index is a running index and num images is 3  When I mess around with    in IPython  it seems to act just like a division sign  i e  one forward slash   I was just wondering if there is any reason for having double forward slashes

User · Answer

To complement these other answers  the    operator also offers significant  3x  performance benefits over    presuming you want integer division    python -m timeit  20 5    2  100 000 000 loops  best of 3  14 9 nsec per loop    python -m timeit  20 5   2   10 000 000 loops  best of 3  48 4 nsec per loop    python -m timeit  20   2   10 000 000 loops  best of 3  43 0 nsec per loop    python -m timeit  20    2  100 000 000 loops  best of 3  14 4 nsec per loop

User · Answer

is unconditionally  quot flooring division quot   e g   gt  gt  gt  4 0  1 5 2 0  As you see  even though both operands are floats     still floors -- so you always know securely what it s going to do  Single   may or may not floor depending on Python release  future imports  and even flags on which Python s run  e g     python2 6 -Qold -c  print 2 3  0   python2 6 -Qnew -c  print 2 3  0 666666666667  As you see  single   may floor  or it may return a float  based on completely non-local issues  up to and including the value of the -Q flag    -   So  if and when you know you want flooring  always use     which guarantees it  If and when you know you don t want flooring  slap a float   around other operand and use    Any other combination  and you re at the mercy of version  imports  and flags -

User · Answer

can be considered an alias to math floor   for divisions with return value of type float  It operates as no-op for divisions with return value of type int   import math   let s examine  float  returns   -------------------------------------   divide  gt  gt  gt  1 0   2 0 5   divide and round down  gt  gt  gt  math floor 1 0 2  0 0   divide and round down  gt  gt  gt  1 0    2 0 0    now let s examine  integer  returns   -------------------------------------  gt  gt  gt  1 2 0  gt  gt  gt  1  2 0

User · Answer

In Python 3  they made the   operator do a floating-point division  and added the    operator to do integer division  i e   quotient without remainder   whereas in Python 2  the   operator was simply integer division  unless one of the operands was already a floating point number  In Python 2 X   gt  gt  gt  10 3 3  gt  gt  gt    To get a floating point number from integer division   gt  gt  gt  10 0 3 3 3333333333333335  gt  gt  gt  float 10  3 3 3333333333333335  In Python 3   gt  gt  gt  10 3 3 3333333333333335  gt  gt  gt  10  3 3  For further reference  see PEP238

User · Answer

To complement Alex s response  I would add that starting from Python 2 2 0a2  from   future   import division is a convenient alternative to using lots of float            All divisions  perform float divisions  except those with      This works with all versions from 2 2 0a2 on

[python] What is the reason for having '//' in Python?

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