Assignment statements

assignmentstatement Assignment statements are used to (re)bind names to values and to modify attributes or items of mutable objects: bindingname rebindingname mutable attributeassignment

assignment_stmt: (target_list "=")+ expression_list
target_list:     target ("," target)* [","]
target:          identifier | "(" target_list ")" | "[" target_list "]"
               | attributeref | subscription | slicing

(See section $[*]$ for the syntax definitions for the last three symbols.) An assignment statement evaluates the expression list (remember that this can be a single expression or a comma-separated list, the latter yielding a tuple) and assigns the single resulting object to each of the target lists, from left to right. expressionlist Assignment is defined recursively depending on the form of the target (list). When a target is part of a mutable object (an attribute reference, subscription or slicing), the mutable object must ultimately perform the assignment and decide about its validity, and may raise an exception if the assignment is unacceptable. The rules observed by various types and the exceptions raised are given with the definition of the object types (see section $[*]$ ). targetlist Assignment of an object to a target list is recursively defined as follows. targetlistassignment

If the target list is a single target: the object is assigned to that target.
If the target list is a comma-separated list of targets: the object must be a tuple with the same number of items as the list contains targets, and the items are assigned, from left to right, to the corresponding targets.

Assignment of an object to a single target is recursively defined as follows.