Python 101 (part 2): If Wishes Were Pythons - Tax Evasion (
Page 2 of 9 )
The first - and
simplest - object type you're likely to encounter is the number. I've already
shown you a few examples of how Python treats numbers last time - but here's a
quick refresher anyway:
Python 1.5.2 (#1, Aug 25 2000, 09:33:37) [GCC 2.96 20000731
(experimental)] on
linux-i386
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> print 24+1
25
>>> print 12*10
120
>>> print 65/5
13
>>> print 15-9
6
>>>
There are four basic number types available in
Python:
Integers: These are plain-vanilla numbers like 23, 5748, -947 and
3; they are also the most commonly-used type.
Floats: These are typically
decimal numbers, although Python also allows you to use the scientific notation
to represent them - for example, 3.67, 98.573 or 5.347e-17.
Long
integers: These are integer values which are too large to be handled by the
regular Integer type - for example, 45734893498L or 53267282982L. Note the
uppercase "L" appended to the end of a long integer, which makes this type
easier to identify.
Complex numbers: You may remember these from algebra
class (I don't, but that's probably because I slept my way through college) -
2.5+0.3j, 4.1-03.j and so on. These numbers can be broken up into "real" and
"imaginary" parts...the "imaginary" part is what you bank, while the "real" part
is what the government takes away in taxes.{mospagebreak title=Putting Two And
Two Together} Most of the time, you'll be working with integers and floats; the
other two types are typically used for specialized applications. And as the
example above demonstrates, Python allows you to add, multiply, divide and
otherwise mess with these numbers via simple arithmetic operators. Here's an
example which demonstrates the important ones:
>>> alpha = 10
>>> beta = 2
>>> # standard stuff
... sum = alpha+beta
>>> sum
12
>>> difference = alpha-beta
>>> difference
8
>>> product = alpha*beta
>>> product
20
>>> quotient = alpha/beta
>>> quotient
5
>>> # non-standard stuff
... remainder = alpha%beta
>>> remainder
0
>>> exponent = alpha**beta
>>> exponent
100
>>>
As with all other programming languages, division and
multiplication take precedence over addition and subtraction, although
parentheses can be used to give a particular operation greater precedence. For
example,
#!/usr/bin/python
print(10 + 2 * 4)
returns 18, while
#!/usr/bin/python
print((10 + 2) * 4)
returns 48.
It should be noted at this point that
Python does not support the popular auto-increment (++) and auto-decrement (--)
operators you may have used in Perl, PHP and JavaScript.
There are also
some built-in functions you can use with Python numbers - the most useful are
abs() and pow(), which return the absolute value of a number and raise one
number to the power of another. Take a look.
>>> alpha = -89
>>> abs(alpha)
89
>>> pow(3,2)
9
>>>
