Division in Python 2.7. and 3.3 [duplicate]

问题:

This question already has an answer here:

• Python division 12 answers

How can I divide two numbers in Python 2.7 and get the result with decimals?

I don\'t get it why there is difference:

in Python 3:

>>> 20/15
1.3333333333333333

in Python 2:

>>> 20/15
1

Isn\'t this a modulo actually?

回答1:

In python 2.7, the / operator is integer division if inputs are integers.

If you want float division (which is something I always prefer), just use this special import:

from __future__ import division

See it here:

>>> 3 / 2
1
>>> from __future__ import division
>>> 3 / 2
1.5
>>>

Integer division is achieved by using //, and modulo by using %

>>> 3 % 2
1
>>> 3 // 1
3
>>>

EDIT

As commented by user2357112, this import has to be done before any other normal import.

回答2:

In Python 3, / is float division

In Python 2, / is integer division (assuming int inputs)

In both 2 and 3, // is integer division

(To get float division in Python 2 requires either of the operands be a float, either as 20. or float(20))

回答3:

In Python 2.x, make sure to have at least one operand of your division in float. Multiple ways you may achieve this as the following examples:

20. / 15
20 / float(15)

回答4:

\"/\" is integer division in python 2 so it is going to round to a whole number. If you would like a decimal returned, just change the type of one of the inputs to float:

float(20)/15 #1.33333333