What is AST in Python? [Explained]

AST stands for “Abstract Syntax Tree.” An Abstract Syntax Tree is a data structure that represents the syntactic structure of a program written in a programming language. In other words, it’s a tree-like structure that breaks down the source code of a Python program into its constituent parts, such as statements, expressions, and operators, while abstracting away some of the lower-level details like punctuation and formatting.

Python’s ast module is part of the Python standard library and provides tools for parsing Python source code into an AST. You can use the ast module to analyze, manipulate, or generate Python code programmatically. This is particularly useful for tasks like code analysis, refactoring, code generation, and various forms of code transformation.

Here’s a basic example of how you might use the ast module in Python:

import ast

# Define a simple Python code snippet
source_code = """
def greet(name):
    print(f"Hello, {name}!")

greet("Alice")
"""

# Parse the source code into an AST
parsed_ast = ast.parse(source_code)

# You can now analyze or manipulate the AST
# For example, you can traverse the tree to find all function definitions
for node in ast.walk(parsed_ast):
    if isinstance(node, ast.FunctionDef):
        print(f"Found a function: {node.name}")Code language: Python (python)

In this example, we first parse a simple Python code snippet into an AST using ast.parse(). Then, we traverse the AST to find and print the names of all the functions defined in the code.

The ast module is a powerful tool for programmatic code analysis and manipulation, and it’s commonly used in tools like linters, code formatters, and static code analyzers.

Is Ast Built Into Python?

Yes, the ast module is built into Python, and it is part of the Python standard library. You don’t need to install any additional packages or libraries to use it. It’s available by default in any Python installation, so you can use it in your Python programs without any special setup.

What does AST parse do in Python?

ast.parse() function is used to parse a string containing Python source code and convert it into an Abstract Syntax Tree (AST) representation. The AST represents the syntactic structure of the code, breaking it down into its constituent parts, such as statements, expressions, and operators, while abstracting away some of the lower-level details like punctuation and formatting.

Here’s how ast.parse() works:

1. Input: You provide a string containing Python source code as the argument to ast.parse(). This can be a single expression, a single statement, or even a complete Python script.
2. Parsing: The ast.parse() function parses the input string and constructs an AST representation of the code. During this process, it analyzes the code’s syntax to understand its structure.
3. AST Representation: The result of ast.parse() is an AST object that represents the parsed code. This AST object is a hierarchical tree-like data structure where each node in the tree corresponds to a specific part of the code. For example, there are nodes for function definitions, variable assignments, loops, and more.

Once you have the AST representation of your code, you can use it for various purposes such as:

• Code Analysis: You can traverse the AST to analyze the structure of the code, find specific patterns, or extract information about variables, functions, and more.
• Code Transformation: You can manipulate the AST to transform the code. For example, you can rewrite parts of the code, add new statements, or remove existing ones.
• Code Generation: You can generate Python code from an AST. This is useful for tools that automatically generate code, such as code generators or transpilers.

Here’s a simple example:

import ast

source_code = "x = 10 + 5"

# Parse the source code into an AST
parsed_ast = ast.parse(source_code)

# Now you can analyze or manipulate the AST
# For example, you can print the AST to see its structure
print(ast.dump(parsed_ast))Code language: Python (python)

In this example, ast.parse() takes the source_code string, parses it into an AST, and then ast.dump() is used to print the AST structure, which would show you the hierarchy of nodes in the tree-like structure.

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