The very Basics of Python

There are a few features of python which are different than other program-

ming languages, and which should be mentioned early on so that subsequent

examples don’t seem confusing. Further information on all of these features

will be provided later, when the topics are covered in depth.

Python statements do not need to end with a special character – the

python interpreter knows that you are done with an individual statement

by the presence of a newline, which will be generated when you press the

“Return” key of your keyboard. If a statement spans more than one line, the

safest course of action is to use a backslash (\) at the end of the line to let

python know that you are going to continue the statement on the next line;

you can continue using backslashes on additional continuation lines. (There

are situations where the backslashes are not needed which will be discussed

later.)

Python provides you with a certain level of freedom when composing a

program, but there are some rules which must always be obeyed. One of

these rules, which some people find very surprising, is that python uses in-

dentation (that is, the amount of white space before the statement itself) to

indicate the presence of loops, instead of using delimiters like curly braces

({}) or keywords (like “begin” and “end”) as in many other languages. The

amount of indentation you use is not important, but it must be consistent

within a given depth of a loop, and statements which are not indented must

begin in the first column. Most python programmers prefer to use an edi-

tor like emacs, which automatically provides consistent indentation; you will

probably find it easier to maintain your programs if you use consistent in-

dentation in every loop, at all depths, and an intelligent editor is very useful

in achieving this.