modify_source.py

import dis
import inspect

def trace():
    print("hello!")


def insert_code(code_to_modify, lines_to_insert, before_line):
    lines = inspect.getsourcelines(code_to_modify)[0]
    line_for_break = lines[before_line]
    spaces = line_for_break[:len(line_for_break)-len(line_for_break.lstrip())]
    lines_insert_indent = []
    for line in lines_to_insert:
        lines_insert_indent.append(spaces + line)
    new_lines = lines[1:before_line] + lines_insert_indent + lines[before_line:]
    res = "".join(new_lines)
    print(res)
    return compile(res, '<string>', 'exec')

my_func = """def foo():
    trace()
    a = 1
    b = 2
"""

code = compile(my_func, '<string>', 'exec')
dis.dis(code)
loc_dict = {}
res = eval(code, {}, loc_dict)
print(loc_dict)
new_frame_obj = list(loc_dict.values())[0]
new_code = new_frame_obj.__code__
dis.dis(new_code)