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Indentation

Unlike most programming languages, where indentation is used simply to improve readability of programs, python uses indentation to signal the beginning and end of blocks of statements, that is, groups of statements which will be executed together based on the value of some condition, or the occurrence of an exception. The first statement of your programs must start in the very first column, and within each indented block, you must be consistent in the amount of indentation you use. Although not strictly required, most python programmers try to be consistent in their indentation from block to block as well. The task of writing properly indented programs is made much easier if you use an editor which is python-aware; emacs and vim are examples of such editors, as well as the IDLE or pythonwin programming environments supplied as part of python distributions.

Although it takes some getting used to, using identation to group statements together has some definite benefits. Since there are no brackets or keywords involved in delineating blocks of statements, no decisions need to be made as to whether the delineators should appear on the same line as program statements, or if they should line up with the beginnings or ends of blocks. The result of this is that most python programs look very similar, even if they were written by different people, making ``foreign'' python programs much easier to read and understand. In addition, since the indentation of a program actually determines its structure, python programs provide easy-to-see visual clues to help you understand what a program is doing.


next up previous contents
Next: Truth, Falsehood and Logical Up: Programming Previous: Assignments   Contents
Phil Spector 2003-11-12