How can I check if my python object is a number

Question

In Java the numeric types all descend from Number so I would use   x instanceof Number     What is the python equivalent

User · Accepted Answer

Test if your variable is an instance of numbers.Number:

>>> import numbers
>>> import decimal
>>> [isinstance(x, numbers.Number) for x in (0, 0.0, 0j, decimal.Decimal(0))]
[True, True, True, True]

This uses ABCs and will work for all built-in number-like classes, and also for all third-party classes if they are worth their salt (registered as subclasses of the Number ABC).

However, in many cases you shouldn't worry about checking types manually - Python is duck typed and mixing somewhat compatible types usually works, yet it will barf an error message when some operation doesn't make sense (4 - "1"), so manually checking this is rarely really needed. It's just a bonus. You can add it when finishing a module to avoid pestering others with implementation details.

This works starting with Python 2.6. On older versions you're pretty much limited to checking for a few hardcoded types.

User · Answer

That s not really how python works  Just use it like you would a number  and if someone passes you something that s not a number  fail  It s the programmer s responsibility to pass in the correct types

User · Answer

Python 2  isinstance x   int  long  float  complex   and not isinstance x  bool   Python 3  isinstance x   int  float  complex   and not isinstance x  bool

User · Answer

Use Number from the numbers module to test isinstance n  Number   available since 2 6    isinstance n  numbers Number    Here it is in action with various kinds of numbers and one non-number    gt  gt  gt  from numbers import Number     from decimal import Decimal     from fractions import Fraction     for n in  2  2 0  Decimal  2 0    complex 2 0   Fraction 2 1    2            print   15s  s     n   repr      isinstance n  Number                 2 True             2 0 True  Decimal  2 0   True           2 0j  True  Fraction 2  1  True              2  False   This is  of course  contrary to duck typing  If you are more concerned about how an object acts rather than what it is  perform your operations as if you have a number and use exceptions to tell you otherwise

User · Answer

Sure you can use isinstance  but be aware that this is not how Python works  Python is a duck typed language  You should not explicitly check your types  A TypeError will be raised if the incorrect type was passed    So just assume it is an int  Don t bother checking

[python] How can I check if my python object is a number?

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