The compile() function is used to compile a source string into a code object. A source string refers to a regular string that contains valid Python code.

The function takes a source string and returns a code object that can be executed by using either exec() or eval() functions.

The  compile function takes 3 required arguments: source , filename and mode.

Syntax:
compile(source, filename, mode)

The source argument is a string containing the Python source code to be compiled.

The filename argument is a string representing the filename (if any) from which the code was read, if not provided, it defaults to '<string>'.

Lastly, the mode is a string specifying  what kind of code object should be created, it is one of  'exec', 'eval' or 'single'. 

ExampleEdit & Run
code_string = "x = [1, 2, 3]\nprint(x)"
exec_code_object = compile(code_string, '', 'exec')

exec(exec_code_object)

code_string2 = "7 *(8  + 9)"
eval_code_object = compile(code_string2, '', 'eval')
print(eval(eval_code_object))

 Visualize 
Output:
[1, 2, 3]
119

[Finished in 0.017961172000013903s]

The difference between the 'exec' and the 'eval' mode is that, the exec mode is used with the exec() function to execute a source string which can be having more than one statements while the 'eval' mode is used with the eval() function which is only capable of evaluating a single expression.

The 'single' mode is used to compile a single interactive statement into a code object, this object can then be executed using either exec() or eval() functions.

ExampleEdit & Run

single mode 

code_string = "print('Hello, World!')"
single_code_object = compile(code_string, '', 'single')

exec(single_code_object)

code_string2 = "1 + 2 + 3"
single_code_object2 = compile(code_string2, '', 'single')

print(eval(single_code_object2))
 Visualize 
Output:
Hello, World!
6
None

[Finished in 0.028825209999922663s]