shikake

shikake is an AST-based library that models the static structures and relationships of Python source code according to consumer-defined, domain-specific structural conventions.

It provides building blocks for working with Python code under your own rules, including transpilation and the design or validation of restricted Python dialects. You can also define custom structures and have designated Python constructs modeled using those structures.

Python syntax validation defaults to CPython's non-executing compilation level (syntax_validation="compile"). Use syntax_validation="ast" to skip compilation checks when modeling AST-parseable restricted dialects; unsupported shikake syntax remains unsupported. This does not execute input code or guarantee runtime correctness.

Development status (Alpha)

shikake is currently in Alpha. Public APIs, specifications, and data structures may change incompatibly without prior notice. See STATUS for current progress.

Core concepts

Rather than preserving Python syntax verbatim, shikake represents selected syntactic information in a form that consumers can interpret for their own purposes.

Model structure

• Kind classifies a syntactic element.
• Structure specifies the roles and shapes of its constituent parts.
• Feature captures orthogonal characteristics, such as async or an explicitly written lazy import modifier.
• Model holds a concrete element according to these definitions.

Trusted external Shikumi declarations or an ExternalDefinitionsBuilder using Python data can add Kinds and Structures, and registered calls are represented by dedicated Models during parsing. External Feature declarations are not currently supported.

Three dimensions of name binding

shikake represents three independent properties of a name's binding:

• introduction: whether the introduction is structurally stable (stable or unstable).
• may_rebind: whether a name may be rebound by a later or repeatable write, or by an augmented assignment.
• may_delete: whether the syntax indicates possible deletion.

For example, x = 1 alone has may_rebind=False; adding x = 2 makes it True. A lone n += 1 does not establish a stable introduction. These are syntactic facts, not predictions of execution, definite assignment, or judgments about code quality.

Static relationship candidates

shikake can report candidate targets of base-class references and same-name method override candidates. These are candidates supported by the AST, not guarantees about runtime targets or method resolution order. See the API Reference for the available results and links to their specifications.

Installation

Python 3.11 or later is required. CI targets Python 3.11–3.15; Python 3.14 t-strings are modeled as distinct Kinds.

python -m pip install shikake

Quick start

import shikake

source = '''
class Counter:
    def __init__(self, start=0):
        self.value = start

    def increase(self, amount):
        if amount > 0:
            self.value += amount
        return self.value

def calculate(values):
    counter = Counter()
    for value in values:
        counter.increase(value)
    return counter.value
'''

root = shikake.parse_source(source)

for model in root.walk():
    print(model.kind.id)
    print([part.role for part in model.parts()])

parse_source() builds a Model from one Python source string, and walk() traverses its composition tree. Kind, Structure, and Feature let consumers classify elements without depending directly on their original AST nodes.

Strict and Partial analysis

• Strict: parse_source() and parse_package() require a complete result and raise on unsupported syntax or invalid structures.
• Partial: inspect_source() and inspect_package() return available results together with diagnostics when full analysis is not possible.

Use Strict analysis when completeness is required, and Partial analysis to inspect unsupported or incomplete inputs. An incomplete Partial result must not be treated as a fully analyzed input. Consult the API Reference for details.

For package analysis, pass an include(path, is_directory) callback to parse_package() or inspect_package() to choose subdirectories and matching source files. Returning False for a directory prunes that entire subtree. The extensions=(".py",) parameter selects source suffixes: (".dot",) chooses only .dot and (".py", ".dot") chooses both. These files must contain Python syntax. By default all regular .py files are included, including those under .venv; shikake does not impose exclusion patterns. See Package input selection.

Optional import permissions

Each parsing/inspection API supports import_policy="unrestricted" (default), "registered_interfaces" (only explicitly imported registered interfaces), and "registered_modules" (registered external modules plus caller-specified allowed_modules=("math", "custom_tools")). registered_modules also permits every explicit registered-interface import. Both restricted modes admit the single directive from __future__ import annotations. Relative imports, including within the analyzed package, remain forbidden: change them to absolute imports and explicitly allow the written module names as needed. allowed_modules names must be NFKC-normalized. These checks compare written absolute module names without importing them and do not provide a security sandbox. See the API Reference.

Source comments (v0.0.2)

The explicit collect_comments(source) API returns SourceComments with immutable Comment records, independently of the AST Model tree:

import shikake

source = "# note\nvalue = 1  # type: int\n"
comments = shikake.collect_comments(source)
model = shikake.parse_source(source).get_nodes("body")[0]
if model.span is not None:
    print(comments.above_line(model.span.line))
    print(comments.on_right_of_line(model.span.line))
    print(comments.in_lines(model.span.line, model.span.end_line))

For a function or class, the first statement of its body block supplies a line for querying comments immediately above that statement only if no code appears before the statement on that same line. For a one-line body such as def f(): return 1, this recipe does not apply. For an assignment statement, span.end_line supplies a line for querying its trailing comment. For example:

import shikake

source = "def f():\n    # body note\n    value = 1  # value note\n    return value\n"
comments = shikake.collect_comments(source)
function = shikake.parse_source(source).get_nodes("body")[0]
first = function.get("body").get_nodes("statements")[0]
if first.span is not None:
    print(comments.above_line(first.span.line))
    print(comments.on_right_of_line(first.span.end_line))

The same body lookup works for class definitions. To verify the same-line precondition, use the same universal-newline behavior as comment collection (CR, LF, CRLF); do not use str.splitlines(), which also splits on form feeds and other characters not considered line breaks by the AST:

import io

lines = io.StringIO(source, newline=None).readlines()
prefix = lines[first.span.line - 1].encode("utf-8")[: first.span.column]
if not prefix.strip():
    print(comments.above_line(first.span.line))

AST columns use UTF-8 byte offsets, so the prefix is measured in encoded bytes.

For a decorated function or class, search above its earliest decorator rather than its def/class line:

import shikake

source = "# definition note\n\n@decorator\ndef decorated():\n    return 1\n"
comments = shikake.collect_comments(source)
function = shikake.parse_source(source).get_nodes("body")[0]
if function.span is not None:
    start = min(
        [function.span.line, *(d.span.line for d in function.get_nodes("decorators") if d.span is not None)]
    )
    print(tuple(comment.text for comment in comments.above_line(start)))
    # ('# definition note',)

Here function.span must be present. These are line-position queries, not attachments of comments to declarations or assignments. For comments within multiline constructs, use in_lines(first, last).

It also supports in_lines(first, last), module_header(), and module_footer(). Blank lines do not interrupt upward search; code lines do. CR, LF, and CRLF all use AST-compatible line numbers. For files with encoding declarations or a UTF-8 BOM, read with tokenize.open(path) and pass the same decoded text to both collect_comments() and parse_source(). A SourceComments result must be obtained from collect_comments(); direct construction and dataclasses.replace() are unsupported. Results for syntactically invalid Python input are not guaranteed across Python versions. Comments are not assigned to particular Models and type comments are not interpreted. Python AST parsing continues with type_comments=False. There is no separate Model-based comment lookup: callers can supply the line numbers from an available Model.span to the existing line queries. The module root and other Models may have span=None. A line query does not establish ownership, distinguish Models sharing a line, or verify that a Model and comments came from the same source. See the API Reference for details.

External structures

Consumers can define custom Kinds and Structures with trusted Shikumi declarations or shikake.external.ExternalDefinitionsBuilder and provide them to the parser. For example, a transpiler may map a Python-facing memory or I/O interface to special operations in its target language.

When their documented conditions are met, explicitly imported calls registered as external operations produce dedicated Models instead of ordinary Python call Models. This is not general-purpose resolution of arbitrary libraries: explicit-import and reserved-name rules constrain recognition. See the External Definitions API.

Using analysis results

Transpilation and restricted-Python validation share a basic pattern: inspect Kind, Structure, and Feature information, optionally consult binding facts and static relationship candidates, and then apply the consumer's own rules to translate or accept/reject the input.

shikake does not define those downstream rules. Models are intended to be obtained from the official parsing APIs; constructing your own Models is unsupported.

Limitations

shikake does not execute source code, evaluate values, infer types, or resolve dynamic names. Models do not aim to reproduce the original Python code perfectly or to establish its runtime semantics. Syntactic inspection alone does not provide a secure execution sandbox.

See the API Reference for individual contracts and the Documentation Policy for how the sources are managed.

Documentation

API Reference | Status | Changelog | Documentation Policy

License

shikake is distributed under the MIT License.