Core Python Programming (2nd Edition)

>>> type(foo) # assumes foo instantiated also
In addition to type(), there is another useful BIF called isinstance(). We cover it more formally in
Chapter 13 (Object-Oriented Programming), but here we can introduce it to show you how you can use
it to help determine the type of an object.
Example
We present a script in Example 4.1 that shows how we can use isinstance() and type() in a runtime
environment. We follow with a discussion of the use of type() and how we migrated to using isinstance
() instead for the bulk of the work in this example.
Example 4.1. Checking the Type (typechk.py)
The function displayNumType() takes a numeric argument and uses the type() built-in to
indicate its type (or "not a number," if that is the case).
1 #!/usr/bin/env python
2
3 def displayNumType(num):
4 print num, 'is',
5 if isinstance(num, (int, long, float, complex)):
6 print 'a number of type:', type(num).__name__
7 else:
8 print 'not a number at all!!'
9
10 displayNumType(-69)
11 displayNumType(9999999999999999999999L)
12 displayNumType(98.6)
13 displayNumType(-5.2+1.9j)
14 displayNumType('xxx')
Running typechk.py, we get the following output:
-69 is a number of type: int
9999999999999999999999 is a number of type: long
98.6 is a number of type: float
(-5.2+1.9j) is a number of type: complex
xxx is not a number at all!!
The Evolution of This Example
Original
The same function was defined quite differently in the first edition of this book: