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

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

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__`.

``>>> from __future__ import division>>> a = 4>>> b = 6>>> c = a / b>>> c0.66666666666666663``

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.

# 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 < 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:

"How do I force true division such that `a / b` will return a fraction?"

In Python 3, to get true division, you simply do `a / b`.

``>>> 1/20.5``

Floor division, the classic division behavior for integers, is now `a // b`:

``>>> 1//20>>> 1//2.00.0``

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:

``>>> from __future__ import division>>> 1/20.5>>> 1//20>>> 1//2.00.0``

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:

``>>> 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:

``>>> from operator import truediv>>> 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.

``>>> 1 / float(2)0.5>>> 1 / float(2j)Traceback (most recent call last):  File "<stdin>", line 1, in <module>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``