lexical conventions and syntax although tabs can be used for indentationthis practice is discouraged the use of spaces is universally preferred (and encouragedby the python programming community when tab characters are encounteredthey're converted into the number of spaces required to move to the next column that' multiple of (for examplea tab appearing in column inserts enough spaces to move to column running python with the - option prints warning messages when tabs and spaces are mixed inconsistently within the same program block the -tt option turns these warning messages into taberror exceptions to place more than one statement on lineseparate the statements with semicolon (; line containing single statement can also be terminated by semicolonalthough this is unnecessary the character denotes comment that extends to the end of the line appearing inside quoted string doesn' start commenthowever finallythe interpreter ignores all blank lines except when running in interactive mode in this casea blank line signals the end of input when typing statement that spans multiple lines identifiers and reserved words an identifier is name used to identify variablesfunctionsclassesmodulesand other objects identifiers can include lettersnumbersand the underscore character (_but must always start with nonnumeric character letters are currently confined to the characters - and - in the iso-latin character set because identifiers are casesensitivefoo is different from foo special symbols such as $%and are not allowed in identifiers in additionwords such as ifelseand for are reserved and cannot be used as identifier names the following list shows all the reserved wordsand as assert break class continue def del elif else except exec finally for from global if import in is lambda nonlocal not or pass print raise return try while with yield identifiers starting or ending with underscores often have special meanings for exampleidentifiers starting with single underscore such as _foo are not imported by the from module import statement identifiers with leading and trailing double underscores such as _init_ are reserved for special methodsand identifiers with leading double underscores such as _bar are used to implement private class membersas described in "classes and object-oriented programming general-purpose use of similar identifiers should be avoided numeric literals there are four types of built-in numeric literalsn booleans integers lib fl ff