conditional break for ipython terminal (**Use:** `if condition: breakpoint` instead -- **don't** use this.)

conditional_breakpoint.py

#  This is for ipython interactive
#  - you can, for example, place this in
#    ~/.ipython/profile_default/startup

def breakpoint_(condition=True):
    '''
    in ipython:
    - breakpoint_() <= break always
    - breakpoint_(False) <= never break
    - breakpoint_(condition) <= break if True
    '''
    # import here, to limit
    # to this function's namespace
    from sys import _getframe
    from IPython.terminal import debugger
    
    if condition:
        debugger.set_trace(_getframe().f_back)
        return debugger

Note: Don't use this - there's no need for it.

if condition:
    breakpoint_()

Is just as good. Also, note: breakpoint() coming with PEP 553 in Python 3.7.

This came via digesting @tillahoffmann post on:
ipython/ipython#9940 (comment)
combined with jupyter docs (and newer merge) here:
http://ipython.readthedocs.io/en/stable/api/generated/IPython.terminal.debugger.html