Python compile() Function

The compile() converts a string to a Python code object. The code object is then executed using exec() function.

Compile source into a code object that can be executed by exec() or eval().

Syntax

Python

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compile(source, filename, mode, flags, dont_inherit, optimize, *, _feature_version: int = ...) -> Any

Parameters

Parameter	Description
`source.`	Required. The string (or byte string) containing the code to compile, or an AST object containing the code.
`filename`	Required. The name of the source file for this code, or any name you wish if the code did not come from a file.
`mode`	Optional. The manner in which the code will be compiled. Accepted values are: 'eval' - source consists of only a single expression. 'exec' - source contains Python statements, class and functions: a full program, in other words. 'single' - source consists of a single interactive statement
`flags`	Optional. controls which compiler flags are enabled. Default Value: 0.
`dont_inherit`	Optional. controls which future features are enabled. Default Value: 0.
`optimize:int`	Optional. optimization level of the compiler. Default value -1.

The code string, source filename or just a name, and the code type ('exec', 'eval', or 'single') must be specified.

Example

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# A code block to be executed:
codeString = 'a = 5\nb = 6\nprint(f"{a} + {b} = {a + b}")'
codeObject = compile(codeString, 'add', 'exec')
exec(codeObject)

# An expression to be evaluated:
codeString = 'print(3 + 11)'
codeObject = compile(codeString, 'add', 'eval')
exec(codeObject)

# An "interactive" statement that will be printed
codeString = '7 * 3'
codeObject = compile(codeString, 'add', 'single')
exec(codeObject)

Output

5 + 6 = 11
14
21

Notes

If variables are assigned in the code string, those variables are available after the code has been executed. This only works with the 'exec' code type.

Example

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# Assign a value to a variable in the code string 
codeString = 'a = 3\nb = 4\nmySum = a + b'
codeObject = compile(codeString, 'add', 'exec')
exec(codeObject)
# We can now use the variables a, b, and mySum
print(f'{a} + {b} = {mySum}')

Output

3 + 4 = 7

You can also reference variables defined outside of the code string.

Example

Python

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# Using a variable defined outside the code string
n = 31.006
codeString = 'cubeRoot = n ** (1./3)'
cubeRootFnc = compile(codeString, 'cubeRoot', 'exec')
exec(cubeRootFnc)
print(f'The cube root of {n} is {cubeRoot}')

Output

The cube root of 31.006 is 3.141583309036842