Save command history in pdb

Question

Is there a way to save pdb (python debugger) command history across sessions? Also, can I specify history length?

This is similar to the question How can I make gdb save the command history?, however for pdb instead of gdb.

-Many thanks

Answer 1

See this post. It is possible to save history in pdb. By default, pdb does not read multiple lines. So all functions need to be on a single line.

In ~/.pdbrc:

import atexit
import os
import readline

historyPath = os.path.expanduser("~/.pyhistory")

def save_history(historyPath=historyPath): import readline; readline.write_history_file(historyPath)

if os.path.exists(historyPath): readline.read_history_file(historyPath)

atexit.register(save_history, historyPath=historyPath)

Answer 2

Credits: https://wiki.python.org/moin/PdbRcIdea

pdb uses readline so we can instruct readline to save history:

.pdbrc

# NB: `pdb` only accepts single-line statements
import os
with open(os.path.expanduser("~/.pdbrc.py")) as _f: _f = _f.read()
exec(_f)
del _f

.pdbrc.py

def _pdbrc_init():
    # Save history across sessions
    import readline
    histfile = ".pdb-pyhist"
    try:
        readline.read_history_file(histfile)
    except IOError:
        pass
    import atexit
    atexit.register(readline.write_history_file, histfile)
    readline.set_history_length(500)

_pdbrc_init()
del _pdbrc_init

---

For the drop-in replacement pdb++, copy the above function code into the setup() method:

from pdb import DefaultConfig, Pdb


class Config(DefaultConfig):
    def setup(self, pdb):
        ## Save history across sessions
        #
        import readline
        ...

Answer 3

An example for clearing / reading / printing the current pdb history:

(Pdb) readline.clear_history()
(Pdb) print('hello pdb')
hello pdb
(Pdb) from pprint import pprint; import readline
(Pdb) y = range(readline.get_current_history_length() + 2)
(Pdb) print([readline.get_history_item(x) for x in y])

output:

[None, 
"print('hello pdb')", 
'from pprint import pprint; import readline', 
'y = range(readline.get_current_history_length() + 2)',
'print([readline.get_history_item(x) for x in y])']

reference:

• https://docs.python.org/2/library/readline.html

two liner without readline.clear_history for what has been input to pdb so far:

from pprint import pprint; import readline
pprint([readline.get_history_item(x) for x in range(readline.get_current_history_length() + 1)])

Answer 4

I don't believe there is a way with "stock" pdb. But I wrote a replacement debugger that does that.

just install Pycopia from source: http://code.google.com/p/pycopia/source/checkout and it's in pycopia.debugger.

Answer 5

Extending @olejorgenb's excellent answer, I wanted the history file in my home directory rather than in the current directory, so I used pathlib.Path.expanduser.

import pdb

class Config(pdb.DefaultConfig):

    def setup(self, pdb):
        # Save history across sessions
        import readline
        from pathlib import Path
        histfile_path = Path("~/.pdb-pyhist").expanduser()

        try:
            readline.read_history_file(histfile_path)
        except IOError:
            pass

        import atexit
        atexit.register(readline.write_history_file, histfile_path)
        readline.set_history_length(500)

This is my setup for configuring pdbpp (an improved debugger, aka pdb++, https://pypi.org/project/pdbpp/). You can use the same idea along with @olejorgenb's answer to configure regular pdb.

Answer 6

I think you can do this with IPython:

http://ipython.org/ipython-doc/stable/interactive/tutorial.html#history

ipdb replacement for pdb:

http://pypi.python.org/pypi/ipdb