Python exec(): Execute Python Code Dynamically

The exec() function runs Python code from a string or a file, allowing for dynamic execution of multiple statements. It’s useful for running scripts, modifying variables dynamically, and executing external Python code.

Example

code = """
x = 10
y = 5
print(x + y)
"""
exec(code)

Output:

15

This executes multiple lines of code dynamically.

Syntax

exec(expression, globals=None, locals=None)

• expression → A string containing valid Python code.
• globals (optional) → A dictionary defining the global scope.
• locals (optional) → A dictionary defining the local scope.

1. Modifying Variables with exec()

You can dynamically update variables using exec().

x = 5
exec("x = x * 2")
print(x)  
# Output: 10

Useful when working with dynamic configuration or variable modification.

2. Running a Function from a String

Define and execute a function from a string.

code = """
def greet(name):
    return f'Hello, {name}!'
"""

exec(code)
print(greet("Alice"))  
# Output: Hello, Alice!

Useful for dynamically generating functions.

3. Executing Code from a File

Run Python code directly from a file.

with open("script.py", "r") as file:
    exec(file.read())

Great for loading external scripts dynamically.

4. Using exec() with Restricted Scope

Limit variable access to prevent unwanted modifications.

safe_scope = {"x": 5}
exec("x = x + 10", safe_scope)
print(safe_scope["x"])  
# Output: 15

This ensures code only modifies allowed variables.

Key Notes

• ✔ Runs multiple lines of Python code dynamically.
• ✔ Modifies variables and defines functions on the fly.
• ✔ Can execute external Python scripts.
• ✔ Use restricted scope (globals, locals) for safety.

By using exec(), you can execute Python code dynamically, making it a powerful tool for automation, scripting, and dynamic programming. 🚀