tions that can be used in static analysis tools and IDEs. 

Changed in version 3.8: Now annotated assignments allow same expressions in the right hand side as the regular assignments. Previously, some expressions (like un-parenthesized tuple expressions) caused a syntax error. 

## 7.3 The $_{assert}$statement 

Assert statements are a convenient way to insert debugging assertions into a program: 

assert_stmt ::= "assert" expression ["," expression ] 

The simple form, assert expression , is equivalent to 

if __debug__: if not expression: raise AssertionError 

The extended form,$_{assert expression1, expression2}$ , is equivalent to 

if __debug__: if not expression1: raise AssertionError (expression2) 

These equivalences assume that __debug__ and AssertionError refer to the built-in variables with those names. In the current implementation, the built-in variable __debug__ is True under normal circumstances, $_{False}$when optimization is requested (command line option$_{-O}$ ). The current code generator emits no code for an assert statement when optimization is requested at compile time. Note that it is unnecessary to include the source code for the expression that failed in the error message; it will be displayed as part of the stack trace. 

Assignments to$_{__debug__}$ are illegal. The value for the built-in variable is determined when the interpreter starts. 

## 7.4 The pass statement 

$_{pass_stmt}$::= "pass" 

$_{pass}$is a null operation — when it is executed, nothing happens. It is useful as a placeholder when a statement is required syntactically, but no code needs to be executed, for example: 

def f(arg): pass # a function that does nothing (yet) classC : pass # a class with no methods (yet) 

## 7.5 The $_{del}$statement 

$_{del_stmt}$::= "del" target_list 

Deletion is recursively defined very similar to the way assignment is defined. Rather than spelling it out in full details, here are some hints. 

Deletion of a target list recursively deletes each target, from left to right. 

Deletion of a name removes the binding of that name from the local or global namespace, depending on whether the name occurs in a$_{global}$ statement in the same code block. If the name is unbound, a$_{NameError}$ exception will be raised. 

Deletion of attribute references, subscriptions and slicings is passed to the primary object involved; deletion of a 

