`compile()`

The built-in compile() function converts a string containing Python code into a code object. This code can be executed using exec() or eval(). This allows for the dynamic execution of Python code stored in strings:

Python
      
>>> code = compile("print('Hello, World!')", "<string>", "exec")
>>> exec(code)
Hello, World!

`compile()` Signature

Python Syntax
      
    
compile(
    source,
    filename,
    mode,
    flags=0,
    dont_inherit=False,
    optimize=-1
)

Arguments

Argument	Description	Default Value
`source`	The source code to compile. It can be a string, byte string, or an AST (abstract syntax tree) object.	Required argument
`filename`	The name of the file from which the code was read. Use `"<string>"` for code in a string.	Required argument
`mode`	Specifies the type of code to compile: `"exec"`, `"eval"`, or `"single"`.	Required argument
`flags`	Compiler options to activate.	`0`
`dont_inherit`	Controls whether to inherit future statements.	`False`
`optimize`	Optimization level of the compiler.	`-1`

Return Value

Returns a code object that can be executed using exec() or evaluated with eval().

`compile()` Examples

With an input expression and eval() to evaluate it:

Python
      
>>> code = compile("5 + 4", "<string>", "eval")
>>> eval(code)
9

With a string containing code and calling exec() to run it:

Python
      
        
      
    
>>> input_string = """
... def greet(name):
...     return f"Hello, {name}!"
...
... print(greet("Jane"))
... """

>>> code = compile(input_string, "<string>", "exec")
>>> exec(code)
Hello, Jane!

`compile()` Common Use Cases

The most common use cases for the compile() function include:

Precompiling expressions or scripts for repeated execution to improve performance
Dynamically executing code received from an external source
Evaluating mathematical expressions or other code snippets stored as strings

Note: The compile() function is a powerful tool that allows you to compile arbitrary Python code that comes to you as strings. To run the resulting code, you can use eval() or exec(), which you must use with extreme care and caution, especially in those cases where the code comes from untrusted sources.

`compile()` Real-World Example

Say that you want to evaluate mathematical expressions stored as strings. Using compile(), you can precompile these expressions and evaluate them multiple times efficiently:

Python
      
        
      
    
>>> import math

>>> expressions = ["3 + 5", "12 / 4", "math.sin(math.pi / 2)"]
>>> compiled_expressions = [
...     compile(expr, "<string>", "eval") for expr in expressions
... ]

>>> results = [eval(code) for code in compiled_expressions]
>>> results
[8, 3.0, 1.0]