Python compile(): Convert Code into Executable Form

Python `compile()`: Convert Code into Executable Form

The compile() function translates Python code (string, file, or AST) into bytecode, which can then be executed using exec() or eval(). This is useful for dynamic code execution, working with files, and optimizing performance.

Simple Example

code = "print('Hello, World!')"
compiled_code = compile(code, "", "exec")
exec(compiled_code)  
# Output: Hello, World!

Here, compile() converts the string into executable bytecode, which is then run using exec().

Syntax

compile(source, filename, mode)

source → Code as a string, file, or AST (Abstract Syntax Tree).
filename → Name of the file or <string> if it’s from a variable.
mode → "exec" for multiple lines, "eval" for a single expression, "single" for a single statement.

1. Using `compile()` with `eval()` for Expression Execution

compile() can be used with eval() when dealing with expressions that return a value.

code = "5 + 10"
compiled_code = compile(code, "", "eval")
result = eval(compiled_code)
print(result)  # Output: 15

Great for calculating dynamic expressions at runtime.

2. Executing Multiple Lines of Code

If you need to run multiple lines, use "exec".

code = """
x = 5
y = 10
print(x + y)
"""
compiled_code = compile(code, "", "exec")
exec(compiled_code)  
# Output: 15

This is helpful when running dynamically generated scripts.

3. Reading and Running Python Code from a File

You can load and execute Python code from a file using compile().

with open("script.py", "r") as f:
    code = f.read()

compiled_code = compile(code, "script.py", "exec")
exec(compiled_code)

Useful when loading and executing external scripts dynamically.

4. Securing `eval()` with `compile()` (Restricted Scope Execution)

When using eval(), you can limit what variables it has access to.

code = "x + y"
compiled_code = compile(code, "", "eval")
safe_scope = {"x": 10, "y": 5}
print(eval(compiled_code, {}, safe_scope))  # Output: 15

This helps prevent security risks by controlling variable access.

Key Notes

✔ Converts Python code into bytecode – allows execution of dynamic code.
✔ Works with exec() and eval() – use for scripts or expressions.
✔ Useful for loading code from files – great for dynamically running scripts.
✔ Can restrict variable scope – improves security when evaluating code.

By using compile(), you can execute dynamic code safely and efficiently, making it a powerful tool for scripting, automation, and runtime execution. 🚀