5.2.4 List displays

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5.2.4 List displays

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

  list_display | ::= | "[" [expression_list | list_comprehension] "]"
  list_comprehension | ::= | expression list_for
  list_for | ::= | "for" target_list "in" old_expression_list [list_iter]
  old_expression_list | ::= | old_expression [("," old_expression)+ [","]]
  list_iter | ::= | list_for | list_if
  list_if | ::= | "if" old_expression [list_iter]

  Download entire grammar as text.

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 reached5.1.

#### Footnotes

... reached5.1
  In Python 2.3, a list comprehension "leaks" the control variables of each "`for`" it contains into the containing scope. However, this behavior is deprecated, and relying on it will not work once this bug is fixed in a future release