Python Programming for Biology: Bioinformatics and Beyond

Figure 4.3.  The flow of program execution with combined conditional statements.

One of the blocks of code ‘a’, ‘b’ or ‘c’ will be executed depending on the truth or

falsehood of statements that follow the ‘if’ and ‘elif’ keywords. If the conditional

expression at the ‘if’ evaluates as true then code block ‘a’ is executed, otherwise if the

conditional expression at ‘elif’ evaluates as true then instead code block ‘b’ is executed,.

Finally, if none of the conditional expressions evaluates as true then code block ‘c’ is

executed (so there is no additional conditional expression to evaluate for this, the block is

just executed).