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Astroid Node Documentation

The modules in this directory exist to explain the attributes (and sometimes the role) of every node used by astroid. Since astroid often have different attributes than the built-in ast module, we have taken care to document all these different nodes here.

A notable exception is the Module node, which is omitted even from Astroid's own node lists, since it is the parent node of every other node.


Every node file is an example (or several examples) that are carefully explained in the file's docstring. Every docstring takes the format:

NodeName astroid node

Explanation of node in ASTs and in Python code generally. More obscure Python 
statements will have more detailed explanations.

    - attribute_name  (type)
        - explanation of attribute

    - attribute_name  -> example_value

Informal Grammar

In the Astroid documentation here, we often use the Expr and Statement names to represent expression and statement nodes, where nodes in each category play similar roles in certain situations. For example, Expr nodes can often be assigned to and values can be loaded from them. On the other hand, Statement nodes are standalone lines (or blocks) of code that usually compose the body of a parent node.

Statement Nodes

  • Assert
  • Assign
  • AsyncFor
  • AsyncFunctionDef
  • AsyncWith
  • AugAssign
  • Break
  • ClassDef
  • Continue
  • Delete
  • Expr (when enclosing an Expr-type node)
  • For
  • FunctionDef
  • Global
  • If
  • Import
  • ImportFrom
  • Nonlocal
  • Pass
  • Raise
  • Return
  • TryExcept
  • TryFinally
  • While
  • With

Expr Nodes

  • Attribute (see below)
  • Await
  • BinOp
  • BoolOp
  • Call
  • Compare
  • Const
  • DelAttr (see below)
  • DelName (see below)
  • Dict
  • DictComp
  • Ellipsis
  • GeneratorExp
  • IfExp
  • Lambda
  • ListComp
  • Name (see below)
  • Set
  • SetComp
  • UnaryOp
  • Yield
  • YieldFrom

These expression nodes are also assignable (can be the target of an Assign, etc.):

  • AssignAttr (see below)
  • AssignName (see below)
  • List
  • Starred
  • Subscript
  • Tuple

Expression Context

All assignable Python and Astroid AST nodes have an attribute called ctx that is used to indicate the context in which the node appears, and may have a value of Load, Store, or Del. (To refer to these collectively, our Astroid docs often refer to an expr_context type of node, so please do not be confused when you see that notation.)

Interestingly, Astroid has two differences from Python builtin ASTs with regards to expression contexts of assignable nodes: the Name and Attribute nodes. These nodes do not have a ctx attribute; instead, the Astroid developers made the decision to split each use of the Name and Attribute nodes in different contexts into completely new node types. That is why the assignable nodes listed above include AssignAttr and AssignName. See the table below for more details.

Node and Context Python version Astroid version
Attribute in Load Attribute with ctx=Load Simple Attribute node
Attribute in Store Attribute with ctx=Store AssignAttr node
Attribute in Del Attribute with ctx=Del DelAttr node
Name in Load Name with ctx=Load Simple Name node
Name in Store Name with ctx=Store AssignName node
Name in Del Name with ctx=Del DelName node

For more information about this change, please see the original issue made by the Astroid developers: