In it's basic form the Python if statement looks like this:
if expression: statements
If expression is true, statements are executed; otherwise statements are skipped. expression can be of any type; it doesn't have to evaluate to
False. The if statement automatically converts expression to
bool(expression) if needed.
Unlike other languages, parenthesis are not required around expression. In fact, it's considered bad style to include them.
If statements consists of a single statement, the whole
if statement may be written as one line:
if expression: statement
if statement can include an
else clause. The
else clause is optional; an
if statement doesn't have to have one.
if expression: statements else: else-statements
The else-statements are executed if none of the other branches of the if statement are executed. In the case above, if expression is false, else-statements are executed.
if statement can include one or more
elif or 'else-if' clauses. These clauses are also optional.
if expression: statements elif elif-1-expression: elif-1-statements elif elif-2-expression: elif-2-statements more elif clauses...
elif clause contains an expression and statements. The
elif statements are only examined if expression is false. The interpretter starts going through the elif conditions from top to bottom until it finds one that is true. It then executes the corresponding statements and exits the if statement.
if Statement in Full
if statement may include both
elif clauses and an
else clause. The complete form of the
if statement looks like this:
if expression: statements elif elif-1-expression: elif-1-statements elif elif-2-expression: elif-2-statements more elif clauses... else: else-statement