Basic experiment with the bdb module

[Gribouillis]

The standard module bdb deserves to be more widely known. I'm experimenting with it.

import bdb
import inspect
import os

class Mydb(bdb.Bdb):
    def head(self, frame):
        return f'{os.path.basename(frame.f_code.co_filename)}: {frame.f_lineno} :'

    def hprint(self, frame, *args, **kwargs):
        print(self.head(frame), *args, **kwargs)

    def user_call(self, frame, arg):
        # arg is None (see the doc of sys.settrace)
        L, n = inspect.getsourcelines(frame)
        self.hprint(frame, f'-> {L[frame.f_lineno - n].rstrip()} {frame.f_locals}')

    def user_line(self, frame):
        L, n = inspect.getsourcelines(frame)
        self.hprint(frame, L[frame.f_lineno - n], end='')

    def user_return(self, frame, value):
        L, n = inspect.getsourcelines(frame)
        self.hprint(frame, f'<- {frame.f_code.co_name}: {value}')

def eggs(x):
    return x + x

def spam(a, b):
    return f'{eggs(b)} {eggs(a)}'

def main():
    x = 2 + 2
    spam(7, 'ham')
    return x

if __name__ == '__main__':
    mydb = Mydb()
    mydb.runcall(main)

Output:
λ python paillasse/pseudopy/tentebdb.py
tentebdb.py: 32 :     x = 2 + 2
tentebdb.py: 33 :     spam(7, 'ham')
tentebdb.py: 28 : -> def spam(a, b): {'a': 7, 'b': 'ham'}
tentebdb.py: 29 :     return f'{eggs(b)} {eggs(a)}'
tentebdb.py: 25 : -> def eggs(x): {'x': 'ham'}
tentebdb.py: 26 :     return x + x
tentebdb.py: 26 : <- eggs: hamham
tentebdb.py: 25 : -> def eggs(x): {'x': 7}
tentebdb.py: 26 :     return x + x
tentebdb.py: 26 : <- eggs: 14
tentebdb.py: 29 : <- spam: hamham 14
tentebdb.py: 34 :     return x
tentebdb.py: 34 : <- main: 4