Parser Tree

The parser tree is returned by calling parso.Grammar.parse().

Note

Note that parso positions are always 1 based for lines and zero based for columns. This means the first position in a file is (1, 0).

Parser Tree Base Classes

Generally there are two types of classes you will deal with: parso.tree.Leaf and parso.tree.BaseNode.

class parso.tree.BaseNode(children: List[parso.tree.NodeOrLeaf])

Bases: parso.tree.NodeOrLeaf

The super class for all nodes. A node has children, a type and possibly a parent node.

children

A list of NodeOrLeaf child nodes.

start_pos

Returns the starting position of the prefix as a tuple, e.g. (3, 4).

Return tuple of int:  (line, column)

get_start_pos_of_prefix()

Returns the start_pos of the prefix. This means basically it returns the end_pos of the last prefix. The get_start_pos_of_prefix() of the prefix + in 2 + 1 would be (1, 1), while the start_pos is (1, 2).

Return tuple of int:  (line, column)

end_pos

Returns the end position of the prefix as a tuple, e.g. (3, 4).

Return tuple of int:  (line, column)

get_code(include_prefix=True)

Returns the code that was the input for the parser for this node.

Parameters:include_prefix – Removes the prefix (whitespace and comments) of e.g. a statement.

get_leaf_for_position(position, include_prefixes=False)

Get the parso.tree.Leaf at position

Parameters:

• position (tuple) – A position tuple, row, column. Rows start from 1
• include_prefixes (bool) – If False, None will be returned if position falls on whitespace or comments before a leaf

Returns:

parso.tree.Leaf at position, or None

get_first_leaf()

Returns the first leaf of a node or itself if this is a leaf.

get_last_leaf()

Returns the last leaf of a node or itself if this is a leaf.

class parso.tree.Leaf(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.tree.NodeOrLeaf

Leafs are basically tokens with a better API. Leafs exactly know where they were defined and what text preceeds them.

value

str() The value of the current token.

prefix

str() Typically a mixture of whitespace and comments. Stuff that is syntactically irrelevant for the syntax tree.

start_pos

Returns the starting position of the prefix as a tuple, e.g. (3, 4).

Return tuple of int:  (line, column)

get_start_pos_of_prefix()

Returns the start_pos of the prefix. This means basically it returns the end_pos of the last prefix. The get_start_pos_of_prefix() of the prefix + in 2 + 1 would be (1, 1), while the start_pos is (1, 2).

Return tuple of int:  (line, column)

get_first_leaf()

Returns the first leaf of a node or itself if this is a leaf.

get_last_leaf()

Returns the last leaf of a node or itself if this is a leaf.

get_code(include_prefix=True)

Returns the code that was the input for the parser for this node.

Parameters:include_prefix – Removes the prefix (whitespace and comments) of e.g. a statement.

end_pos

Returns the end position of the prefix as a tuple, e.g. (3, 4).

Return tuple of int:  (line, column)

All nodes and leaves have these methods/properties:

class parso.tree.NodeOrLeaf

Bases: object

The base class for nodes and leaves.

type = None

The type is a string that typically matches the types of the grammar file.

parent

The parent BaseNode of this node or leaf. None if this is the root node.

get_root_node()

Returns the root node of a parser tree. The returned node doesn’t have a parent node like all the other nodes/leaves.

get_next_sibling()

Returns the node immediately following this node in this parent’s children list. If this node does not have a next sibling, it is None

get_previous_sibling()

Returns the node immediately preceding this node in this parent’s children list. If this node does not have a previous sibling, it is None.

get_previous_leaf()

Returns the previous leaf in the parser tree. Returns None if this is the first element in the parser tree.

get_next_leaf()

Returns the next leaf in the parser tree. Returns None if this is the last element in the parser tree.

start_pos

Returns the starting position of the prefix as a tuple, e.g. (3, 4).

Return tuple of int:  (line, column)

end_pos

Returns the end position of the prefix as a tuple, e.g. (3, 4).

Return tuple of int:  (line, column)

get_start_pos_of_prefix()

Returns the start_pos of the prefix. This means basically it returns the end_pos of the last prefix. The get_start_pos_of_prefix() of the prefix + in 2 + 1 would be (1, 1), while the start_pos is (1, 2).

Return tuple of int:  (line, column)

get_first_leaf()

Returns the first leaf of a node or itself if this is a leaf.

get_last_leaf()

Returns the last leaf of a node or itself if this is a leaf.

get_code(include_prefix=True)

Returns the code that was the input for the parser for this node.

Parameters:include_prefix – Removes the prefix (whitespace and comments) of e.g. a statement.

search_ancestor(*node_types) → Optional[parso.tree.BaseNode]

Recursively looks at the parents of this node or leaf and returns the first found node that matches node_types. Returns None if no matching node is found.

Parameters:node_types – type names that are searched for.

dump(*, indent: Union[str, int, None] = 4) → str

Returns a formatted dump of the parser tree rooted at this node or leaf. This is mainly useful for debugging purposes.

The indent parameter is interpreted in a similar way as ast.dump(). If indent is a non-negative integer or string, then the tree will be pretty-printed with that indent level. An indent level of 0, negative, or "" will only insert newlines. None selects the single line representation. Using a positive integer indent indents that many spaces per level. If indent is a string (such as "\t"), that string is used to indent each level.

Parameters:indent – Indentation style as described above. The default indentation is 4 spaces, which yields a pretty-printed dump.

>>> import parso
>>> print(parso.parse("lambda x, y: x + y").dump())
Module([
    Lambda([
        Keyword('lambda', (1, 0)),
        Param([
            Name('x', (1, 7), prefix=' '),
            Operator(',', (1, 8)),
        ]),
        Param([
            Name('y', (1, 10), prefix=' '),
        ]),
        Operator(':', (1, 11)),
        PythonNode('arith_expr', [
            Name('x', (1, 13), prefix=' '),
            Operator('+', (1, 15), prefix=' '),
            Name('y', (1, 17), prefix=' '),
        ]),
    ]),
    EndMarker('', (1, 18)),
])

Python Parser Tree

This is the syntax tree for Python 3 syntaxes. The classes represent syntax elements like functions and imports.

All of the nodes can be traced back to the Python grammar file. If you want to know how a tree is structured, just analyse that file (for each Python version it’s a bit different).

There’s a lot of logic here that makes it easier for Jedi (and other libraries) to deal with a Python syntax tree.

By using parso.tree.NodeOrLeaf.get_code() on a module, you can get back the 1-to-1 representation of the input given to the parser. This is important if you want to refactor a parser tree.

>>> from parso import parse
>>> parser = parse('import os')
>>> module = parser.get_root_node()
>>> module
<Module: @1-1>

Any subclasses of Scope, including Module has an attribute iter_imports:

>>> list(module.iter_imports())
[<ImportName: import os@1,0>]

Changes to the Python Grammar

A few things have changed when looking at Python grammar files:

• Param does not exist in Python grammar files. It is essentially a part of a parameters node. parso splits it up to make it easier to analyse parameters. However this just makes it easier to deal with the syntax tree, it doesn’t actually change the valid syntax.
• A few nodes like lambdef and lambdef_nocond have been merged in the syntax tree to make it easier to do deal with them.

Parser Tree Classes

class parso.python.tree.DocstringMixin

Bases: object

get_doc_node()

Returns the string leaf of a docstring. e.g. r'''foo'''.

class parso.python.tree.PythonMixin

Bases: object

Some Python specific utilities.

get_name_of_position(position)

Given a (line, column) tuple, returns a Name or None if there is no name at that position.

class parso.python.tree.PythonLeaf(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.PythonMixin, parso.tree.Leaf

get_start_pos_of_prefix()

Basically calls parso.tree.NodeOrLeaf.get_start_pos_of_prefix().

class parso.python.tree.PythonBaseNode(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonMixin, parso.tree.BaseNode

class parso.python.tree.PythonNode(type, children)

Bases: parso.python.tree.PythonMixin, parso.tree.Node

class parso.python.tree.PythonErrorNode(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonMixin, parso.tree.ErrorNode

class parso.python.tree.PythonErrorLeaf(token_type, value, start_pos, prefix='')

Bases: parso.tree.ErrorLeaf, parso.python.tree.PythonLeaf

class parso.python.tree.EndMarker(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree._LeafWithoutNewlines

type = 'endmarker'

class parso.python.tree.Newline(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.PythonLeaf

Contains NEWLINE and ENDMARKER tokens.

type = 'newline'

class parso.python.tree.Name(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree._LeafWithoutNewlines

A string. Sometimes it is important to know if the string belongs to a name or not.

type = 'name'

is_definition(include_setitem=False)

Returns True if the name is being defined.

get_definition(import_name_always=False, include_setitem=False)

Returns None if there’s no definition for a name.

Parameters:import_name_always – Specifies if an import name is always a definition. Normally foo in from foo import bar is not a definition.

class parso.python.tree.Literal(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.PythonLeaf

class parso.python.tree.Number(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.Literal

type = 'number'

class parso.python.tree.String(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.Literal

type = 'string'

string_prefix

class parso.python.tree.FStringString(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.PythonLeaf

f-strings contain f-string expressions and normal python strings. These are the string parts of f-strings.

type = 'fstring_string'

class parso.python.tree.FStringStart(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.PythonLeaf

f-strings contain f-string expressions and normal python strings. These are the string parts of f-strings.

type = 'fstring_start'

class parso.python.tree.FStringEnd(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree.PythonLeaf

f-strings contain f-string expressions and normal python strings. These are the string parts of f-strings.

type = 'fstring_end'

class parso.python.tree.Operator(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree._LeafWithoutNewlines, parso.python.tree._StringComparisonMixin

type = 'operator'

class parso.python.tree.Keyword(value: str, start_pos: Tuple[int, int], prefix: str = '')

Bases: parso.python.tree._LeafWithoutNewlines, parso.python.tree._StringComparisonMixin

type = 'keyword'

class parso.python.tree.Scope(children)

Bases: parso.python.tree.PythonBaseNode, parso.python.tree.DocstringMixin

Super class for the parser tree, which represents the state of a python text file. A Scope is either a function, class or lambda.

iter_funcdefs()

Returns a generator of funcdef nodes.

iter_classdefs()

Returns a generator of classdef nodes.

iter_imports()

Returns a generator of import_name and import_from nodes.

get_suite()

Returns the part that is executed by the function.

class parso.python.tree.Module(children)

Bases: parso.python.tree.Scope

The top scope, which is always a module. Depending on the underlying parser this may be a full module or just a part of a module.

type = 'file_input'

get_used_names()

Returns all the Name leafs that exist in this module. This includes both definitions and references of names.

class parso.python.tree.Decorator(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

type = 'decorator'

class parso.python.tree.ClassOrFunc(children)

Bases: parso.python.tree.Scope

name

Returns the Name leaf that defines the function or class name.

get_decorators()

Return type:list of Decorator

class parso.python.tree.Class(children)

Bases: parso.python.tree.ClassOrFunc

Used to store the parsed contents of a python class.

type = 'classdef'

get_super_arglist()

Returns the arglist node that defines the super classes. It returns None if there are no arguments.

class parso.python.tree.Function(children)

Bases: parso.python.tree.ClassOrFunc

Used to store the parsed contents of a python function.

Children:

0. <Keyword: def>
1. <Name>
2. parameter list (including open-paren and close-paren <Operator>s)
3. or 5. <Operator: :>
4. or 6. Node() representing function body
3. -> (if annotation is also present)
4. annotation (if present)

type = 'funcdef'

get_params()

Returns a list of Param().

name

Returns the Name leaf that defines the function or class name.

iter_yield_exprs()

Returns a generator of yield_expr.

iter_return_stmts()

Returns a generator of return_stmt.

iter_raise_stmts()

Returns a generator of raise_stmt. Includes raise statements inside try-except blocks

is_generator()

Return bool:Checks if a function is a generator or not.

annotation

Returns the test node after -> or None if there is no annotation.

class parso.python.tree.Lambda(children)

Bases: parso.python.tree.Function

Lambdas are basically trimmed functions, so give it the same interface.

Children:

 0. <Keyword: lambda>
 *. <Param x> for each argument x
-2. <Operator: :>
-1. Node() representing body

type = 'lambdef'

name

Raises an AttributeError. Lambdas don’t have a defined name.

annotation

Returns None, lambdas don’t have annotations.

class parso.python.tree.Flow(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

class parso.python.tree.IfStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Flow

type = 'if_stmt'

get_test_nodes()

E.g. returns all the test nodes that are named as x, below:

if x:

pass

elif x:

pass

get_corresponding_test_node(node)

Searches for the branch in which the node is and returns the corresponding test node (see function above). However if the node is in the test node itself and not in the suite return None.

is_node_after_else(node)

Checks if a node is defined after else.

class parso.python.tree.WhileStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Flow

type = 'while_stmt'

class parso.python.tree.ForStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Flow

type = 'for_stmt'

get_testlist()

Returns the input node y from: for x in y:.

get_defined_names(include_setitem=False)

class parso.python.tree.TryStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Flow

type = 'try_stmt'

get_except_clause_tests()

Returns the test nodes found in except_clause nodes. Returns [None] for except clauses without an exception given.

class parso.python.tree.WithStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Flow

type = 'with_stmt'

get_defined_names(include_setitem=False)

Returns the a list of Name that the with statement defines. The defined names are set after as.

get_test_node_from_name(name)

class parso.python.tree.Import(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

get_path_for_name(name)

The path is the list of names that leads to the searched name.

Return list of Name:  

is_nested()

is_star_import()

class parso.python.tree.ImportFrom(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Import

type = 'import_from'

get_defined_names(include_setitem=False)

Returns the a list of Name that the import defines. The defined names are set after import or in case an alias - as - is present that name is returned.

get_from_names()

level

The level parameter of __import__.

get_paths()

The import paths defined in an import statement. Typically an array like this: [<Name: datetime>, <Name: date>].

Return list of list of Name:  

class parso.python.tree.ImportName(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.Import

For import_name nodes. Covers normal imports without from.

type = 'import_name'

get_defined_names(include_setitem=False)

Returns the a list of Name that the import defines. The defined names is always the first name after import or in case an alias - as - is present that name is returned.

level

The level parameter of __import__.

get_paths()

is_nested()

This checks for the special case of nested imports, without aliases and from statement:

import foo.bar

class parso.python.tree.KeywordStatement(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

For the following statements: assert, del, global, nonlocal, raise, return, yield.

pass, continue and break are not in there, because they are just simple keywords and the parser reduces it to a keyword.

type

Keyword statements start with the keyword and end with _stmt. You can crosscheck this with the Python grammar.

keyword

get_defined_names(include_setitem=False)

class parso.python.tree.AssertStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.KeywordStatement

assertion

class parso.python.tree.GlobalStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.KeywordStatement

get_global_names()

class parso.python.tree.ReturnStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.KeywordStatement

class parso.python.tree.YieldExpr(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

type = 'yield_expr'

class parso.python.tree.ExprStmt(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode, parso.python.tree.DocstringMixin

type = 'expr_stmt'

get_defined_names(include_setitem=False)

Returns a list of Name defined before the = sign.

get_rhs()

Returns the right-hand-side of the equals.

yield_operators()

Returns a generator of +=, =, etc. or None if there is no operation.

class parso.python.tree.NamedExpr(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

type = 'namedexpr_test'

get_defined_names(include_setitem=False)

class parso.python.tree.Param(children, parent=None)

Bases: parso.python.tree.PythonBaseNode

It’s a helper class that makes business logic with params much easier. The Python grammar defines no param node. It defines it in a different way that is not really suited to working with parameters.

type = 'param'

star_count

Is 0 in case of foo, 1 in case of *foo or 2 in case of **foo.

default

The default is the test node that appears after the =. Is None in case no default is present.

annotation

The default is the test node that appears after :. Is None in case no annotation is present.

name

The Name leaf of the param.

get_defined_names(include_setitem=False)

position_index

Property for the positional index of a paramter.

get_parent_function()

Returns the function/lambda of a parameter.

get_code(include_prefix=True, include_comma=True)

Like all the other get_code functions, but includes the param include_comma.

Parameters:bool (include_comma) – If enabled includes the comma in the string output.

class parso.python.tree.SyncCompFor(children: List[parso.tree.NodeOrLeaf])

Bases: parso.python.tree.PythonBaseNode

type = 'sync_comp_for'

get_defined_names(include_setitem=False)

Returns the a list of Name that the comprehension defines.

parso.python.tree.CompFor

alias of parso.python.tree.SyncCompFor

class parso.python.tree.UsedNamesMapping(dct)

Bases: collections.abc.Mapping

This class exists for the sole purpose of creating an immutable dict.

Utility

parso.tree.search_ancestor(node: parso.tree.NodeOrLeaf, *node_types) → Optional[parso.tree.BaseNode]

Recursively looks at the parents of a node and returns the first found node that matches node_types. Returns None if no matching node is found.

This function is deprecated, use NodeOrLeaf.search_ancestor() instead.

Parameters:

• node – The ancestors of this node will be checked.
• node_types – type names that are searched for.