astunparse

The following example demonstrates how to use inspect to get the source of a module, parse it into an AST, and then use astunparse to both reconstruct the source and print a pretty-printed version of the tree.

import inspect
import ast
import astunparse

# get back the source code
astunparse.unparse(ast.parse(inspect.getsource(ast)))

# get a pretty-printed dump of the AST
astunparse.dump(ast.parse(inspect.getsource(ast)))

You can install astunparse directly from the command line using easy_install.

$ easy_install astunparse

If you use virtualenvwrapper, you can create a dedicated environment for astunparse and install it using pip.

$ mkvirtualenv astunparse
$ pip install astunparse

To use astunparse in your Python project, import the module and use the unparse function to convert an Abstract Syntax Tree (AST) back into source code.

import astunparse

# Use the unparse function to convert an AST tree back to source code
# source = astunparse.unparse(ast_tree)

When Python's ast module encounters extremely large float or imaginary literals, it often converts them into inf (infinity) within the AST. To prevent losing the original literal representation during unparsing, astunparse uses a special constant INFSTR to represent these values.

This ensures that the unparser can attempt to reconstruct a valid (though potentially approximate) representation of the original overflowing values.

Use astunparse.dump() to generate a human-readable, pretty-printed string representation of a Python AST. This is useful for debugging and inspecting the structure of the tree.

import ast
import astunparse

# Assuming 'tree' is an AST object
print(astunparse.dump(tree))

Use astunparse.unparse() to convert an Abstract Syntax Tree (AST) back into its original Python source code representation. This is a factored-out version of the unparse utility found in the Python source distribution.

import ast
import astunparse

# Assuming 'tree' is an AST object
source_code = astunparse.unparse(tree)

When instantiating the Printer class, you can control where the output is written and how the tree is indented:

• file: A file-like object where the output will be written. Defaults to sys.stdout.
• indent: The string used for each level of indentation. Defaults to `

The unparse.py script can be executed directly from the terminal to process files.

Basic Usage: Provide one or more paths to Python source files to unparse them to stdout.

python unparse.py <path_to_source_file>

Testing Mode: Use the --testdir flag to run roundtrip tests on all .py files within specified directories.

python unparse.py --testdir <directory_path>

Use dump(tree) to generate a formatted, pretty-printed string representation of a Python AST. This function uses the Printer class to traverse the tree and returns the output as a string.

import ast
import astunparse

tree = ast.parse('x = 1 + 2')
dump_str = astunparse.dump(tree)
print(dump_str)

Use unparse(tree) to convert a Python Abstract Syntax Tree (AST) back into its original source code string. This function wraps the Unparser class and returns the resulting string.

import ast
import astunparse

tree = ast.parse('print("hello world")')
source = astunparse.unparse(tree)
print(source)