How can I force division to be floating point Division keeps rounding down to 0

Question

I have two integer values a and b  but I need their ratio in floating point   I know that a  lt  b and I want to calculate a   b  so if I use integer division I ll always get 0 with a remainder of a   How can I force c to be a floating point number in Python in the following   c   a   b

User · Answer

from operator import truediv  c   truediv a  b

User · Answer

Just making any of the parameters for division in floating-point format also produces the output in floating-point   Example    gt  gt  gt  4 0 3 1 3333333333333333   or    gt  gt  gt  4   3 0 1 3333333333333333   or     gt  gt  gt  4   float 3  1 3333333333333333   or     gt  gt  gt  float 4    3 1 3333333333333333

User · Answer

from operator import truediv  c   truediv a  b    where a is dividend and b is the divisor  This function is handy when quotient after division  of two integers is a float

User · Answer

In Python 2  division of two ints produces an int  In Python 3  it produces a float  We can get the new behaviour by importing from   future      gt  gt  gt  from   future   import division  gt  gt  gt  a   4  gt  gt  gt  b   6  gt  gt  gt  c   a   b  gt  gt  gt  c 0 66666666666666663

User · Answer

If you want to use  true   floating point  division by default  there is a command line flag   python -Q new foo py   There are some drawbacks  from the PEP       It has been argued that a command line option to change the         default is evil   It can certainly be dangerous in the wrong         hands  for example  it would be impossible to combine a 3rd         party library package that requires -Qnew with another one that         requires -Qold     You can learn more about the other flags values that change   warn-about the behavior of division by looking at the python man page   For full details on division changes read  PEP 238 -- Changing the Division Operator

User · Answer

c   a    b   1 0

User · Answer

This will also work   gt  gt  gt  u 1  5  gt  gt  gt  print u 0 2

User · Answer

Add a dot     to indicate floating point numbers   gt  gt  gt  4 3  1 3333333333333333

User · Answer

How can I force division to be floating point in Python  I have two integer values a and b  but I need their ratio in floating point  I know that a  lt  b and I want to calculate a b  so if I use integer division I ll always get 0 with a remainder of a  How can I force c to be a floating point number in Python in the following  c   a   b   What is really being asked here is   quot How do I force true division such that a   b will return a fraction  quot  Upgrade to Python 3 In Python 3  to get true division  you simply do a   b   gt  gt  gt  1 2 0 5  Floor division  the classic division behavior for integers  is now a    b   gt  gt  gt  1  2 0  gt  gt  gt  1  2 0 0 0  However  you may be stuck using Python 2  or you may be writing code that must work in both 2 and 3  If Using Python 2 In Python 2  it s not so simple  Some ways of dealing with classic Python 2 division are better and more robust than others  Recommendation for Python 2 You can get Python 3 division behavior in any given module with the following import at the top  from   future   import division  which then applies Python 3 style division to the entire module  It also works in a python shell at any given point  In Python 2   gt  gt  gt  from   future   import division  gt  gt  gt  1 2 0 5  gt  gt  gt  1  2 0  gt  gt  gt  1  2 0 0 0  This is really the best solution as it ensures the code in your module is more forward compatible with Python 3  Other Options for Python 2 If you don t want to apply this to the entire module  you re limited to a few workarounds  The most popular is to coerce one of the operands to a float  One robust solution is a    b   1 0   In a fresh Python shell   gt  gt  gt  1  2   1 0  0 5  Also robust is truediv from the operator module operator truediv a  b   but this is likely slower because it s a function call   gt  gt  gt  from operator import truediv  gt  gt  gt  truediv 1  2  0 5  Not Recommended for Python 2 Commonly seen is a   float b   This will raise a TypeError if b is a complex number  Since division with complex numbers is defined  it makes sense to me to not have division fail when passed a complex number for the divisor   gt  gt  gt  1   float 2  0 5  gt  gt  gt  1   float 2j  Traceback  most recent call last     File  quot  lt stdin gt  quot   line 1  in  lt module gt  TypeError  can t convert complex to float  It doesn t make much sense to me to purposefully make your code more brittle  You can also run Python with the -Qnew flag  but this has the downside of executing all modules with the new Python 3 behavior  and some of your modules may expect classic division  so I don t recommend this except for testing  But to demonstrate    python -Qnew -c  print 1 2  0 5   python -Qnew -c  print 1 2j  -0 5j

User · Answer

In Python 3 x  the single slash     always means true  non-truncating  division   The    operator is used for truncating division   In Python 2 x  2 2 and above   you can get this same behavior by putting a  from   future   import division   at the top of your module

User · Answer

You can cast to float by doing c   a   float b   If the numerator or denominator is a float  then the result will be also     A caveat  as commenters have pointed out  this won t work if b might be something other than an integer or floating-point number  or a string representing one   If you might be dealing with other types  such as complex numbers  you ll need to either check for those or use a different method

[python] How can I force division to be floating point? Division keeps rounding down to 0?

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