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5.2.4 List displays

A list display is a possibly empty series of expressions enclosed in square brackets:

test or_test | lambda_form

testlist test ( "," test )* [ "," ]

list_display "[" [ listmaker ] "]"

listmaker expression ( list_for

| ( "," expression )* [ "," ] )

list_iter list_for | list_if

list_for "for" expression_list "in" testlist

[ list_iter ]

list_if "if" test [ list_iter ]

A list display yields a new list object. Its contents are specified by providing either a list of expressions or a list comprehension. When a comma-separated list of expressions is supplied, its elements are evaluated from left to right and placed into the list object in that order. When a list comprehension is supplied, it consists of a single expression followed by at least one for clause and zero or more for or if clauses. In this case, the elements of the new list are those that would be produced by considering each of the for or if clauses a block, nesting from left to right, and evaluating the expression to produce a list element each time the innermost block is reached⁽¹⁰⁾.