Python 101 (part 1): Snake Eyes - Milk And Toast And Honey (
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Like every programming language
worth its salt, Python allows you to assign values to variables, the fundamental
building blocks of any programming languages. Think of a variable as a container
which can be used to store data; this data is used in different places in your
Python program.
A variable can store both numeric and non-numeric data, and the contents of a
variable can be altered during program execution. Finally, variables can be compared
with each other, and you - the programmer - can write program code that performs
specific actions on the basis of this comparison.
The manner in which variables are assigned values should be clear from the following
example:
>>> alpha = 99
>>> print alpha
99
>>> beta = 2
>>> print beta
2
>>> gamma =
"Milk and toast and honey"
>>> print gamma
Milk and toast and honey
>>>
Although assigning values to a variable is extremely simple - as you've just
seen - there are a few things that you should keep in mind here:
* Every variable name must begin with a letter or underscore character (_), optionally
followed by more letters or numbers - for example, "a", "data123", "i_am_god"
* Case is important when referring to variables - in Python, a "cigar" is definitely
not a "CIGAR"!
* The equals (=) sign is used to assign a value to a variable.
* It's always a good idea to give your variables names that make sense and are
immediately recognizable - it's easy to tell what "net_profit" refers to, but
not that easy to identify "np".
* Unlike Java and C, Python does not require you to declare the type of variable
prior to assigning it a value. It's behaviour here is closer to PHP, which allows
you to assign any type of value to a variable without declaring it first.
* Also like PHP, variables are created when they are assigned values - it is
not necessary to declare them first.
* Finally, Python variable names are not preceded with a $ sign, unlike most
of its counterparts. Once you get used to it, you'll find that this actually adds
to readability.
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