Python compile() function takes source code as input and returns a code object which is ready to be executed and which can later be executed by the exec() function.
Syntax compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)
Parameters:
- Source – It can be a normal string, a byte string, or an AST object
- Filename -This is the file from which the code was read. If it wasn’t read from a file, you can give a name yourself.
- Mode – Mode can be exec, eval or single.
- a. eval – If the source is a single expression.
- b. exec – It can take a block of a code that has Python statements, class and functions and so on.
- c. single – It is used if consists of a single interactive statement
- Flags (optional) and dont_inherit (optional) – Default value=0. It takes care that which future statements affect the compilation of the source.
- Optimize (optional) – It tells optimization level of compiler. Default value -1.
Python compile() function example
Example 1: Simple compile() example in Python.
Here filename is mulstring and exec mode allows the use of exec() method and the compile method converts the string to Python code object.
Python3
# Python code to demonstrate working of compile().# Creating sample sourcecode to multiply two variables# x and y.srcCode = 'x = 10\ny = 20\nmul = x * y\nprint("mul =", mul)'# Converting above source code to an executableexecCode = compile(srcCode, 'mulstring', 'exec')# Running the executable code.exec(execCode) |
Output:
mul = 200
Example 2: Another demonstration working of compile
Python
# Another Python code to demonstrate working of compile().x = 50# Note eval is used for single statementa = compile('x', 'test', 'single')print(type(a))exec(a) |
Output:
<class 'code'> 50
Example 3: Python compile function from file
In this example, we will take main.py file with some string display methods, and then we read the file content and compile it to code the object and execute it.
main.py:
Python3
String = "Welcome to GeeksforLazyroar"print(String) |
Code: Here we will read the file content as a string and then compile it to a code object.
Python3
# reading code from a filef = open('main.py', 'r')temp = f.read()f.close()code = compile(temp, 'main.py', 'exec')exec(code) |
Output:
Welcome to GeeksforLazyroar
Example 4: Compile() with eval()
Here eval is used when the source is a single expression.
Python3
# Another Python code to demonstrate# working of compile() with eval.x = 50# Note eval is used for statementa = compile('x == 50', '', 'eval')print(eval(a)) |
Output:
True
Applications:
- If the Python code is in string form or is an AST object, and you want to change it to a code object, then you can use compile() method.
- The code object returned by the compile() method can later be called using methods like: exec() and eval() which will execute dynamically generated Python code.
