[BangPypers] using IPython from pdb

[Jeffrey Jose]

Thanks. I'll give it a spin.

btw, Can you tell me why you prefer bpython over IPython and the nifty
features I should be looking for when I try bpython ?


Jeff

On Sat, Feb 6, 2010 at 7:55 PM, Shashwat Anand <anand.shashwat at gmail.com>wrote:

> @Jeffrey,
>
> bpython is a bit unstable and crash-prone but I prefer it over Ipython.
>
> On Sat, Feb 6, 2010 at 7:45 PM, Jeffrey Jose <jeffjosejeff at gmail.com>
> wrote:
>
> > [ caution, huge email follows ]
> >
> > Hey Senthil,
> > I was under the impression that everyone here used and loved IPython.
> Boy,
> > was I wrong.
> > I wont attempt to convince you folks why you should use IPython, but here
> a
> > few features that I love in IPython which are not there (or not  very
> > obvious) in vanilla python interpreter.
> >
> > note: I'm using ">>" for prompt, you can always customize your IPython
> > interpreter.
> >
> > *Tab completion*. I cant live without it.
> >
>
> bpython supports tab-completion
>
>
> > >> import sys
> > >> sy<TAB>
> > >> sys.<TAB>
> > sys.foo sys.bar sys.baz
> >
> > >> sys.getsi<TAB>
> > >> sys.getsizeof
> >
> > *Documentation* and *Function Signature*
> >
>
> bpython supports these features
>
>
> > >> sys.getsizeof?
> > *Type*:             builtin_function_or_method
> > *Base Class*:  <type 'builtin_function_or_method'>
> > *String Form*:  <built-in function getsizeof>
> > *Namespace*:   Interactive
> > *Docstring*:
> >     getsizeof(object, default) -> int
> >
> >     Return the size of object in bytes
> >
> > *Source Code*
> > >> import multiprocessing
> > >> multiprocessing.os?
> > *[Doc, Function Signature etc]*
> >
> > >> multiprocessing.os??
> > *[opens the source code if you wanna browse around]*
> >
> >
> > Those are the top 3 things that I love about IPython interpreter. And
> ever
> > since I found them, I haven't gone back to vanilla python interpreter.
> >
> > Senthil wrote,
> >
> > * I am really not sure as how using IPython from pdb can help during
> > debugging? I tried it, I loose all the pdb's capabilities when I enter
> into
> > the IPython shell. How do people normally use it?
> > *
> >
> > Yes, you're right. You loose all capabilities of pdb when you're in
> IPython
> > (there's a solution, i'll get to that later)
> > Here's my typical IPython from pdb session for debugging.
> >
> > 1. Insert import pdb;pdb.set_trace() the place where I suspect the
> problem
> > is. Assume the very next line throws a huge error.
> > 2. Run the code, drop into pdb
> > 3. Invoke IPython from pdb
> > >> whos
> > # Shows all the variables in the current context
> > 4. Poke around a lil bit, see what's the values of variables are, etc
> etc.
> > Pretty normal stuff. Couple this with IPython's excellent introspective
> > power you can rip apart and dig each and everything.
> > >> import more_modules
> > >> try_different_things(); try_different_logic();
> > 5. Execute the "next line" and expect it to throw the error. See the
> error,
> > if you want, retry the same line, try different arguments. Note: You
> havent
> > progressed a line at all, you're just trying out stuff at this moment
> > 6. Once you're done your bit, you *get out of IPython. Cntrl-D*
> > 7*. *Back in pdb, use all of pdb's power. Step in, Execute next line, set
> > more breakpoints, etc etc
> > 8. Hit "c" to proceed to next breakpoint.
> > 9. Repeat Steps 3 -> 8
> >
> > I've never had to use print statements for debugging ever since I found
> > pdb.
> > With print, you can print only a couple of variables, with IPython (pdb
> > actually) you have access to the entire namespace. IPython just makes
> > working with the huge namespace a breeze.
> >
> > If you arent bored already, I'll explain a unique (weird ?) way I write
> > code
> > these days.
> > Normally, we have 2 windows open. One python interpreter and your fav
> text
> > editor. You try out stuff before to type it in your text editor.
> > Here's a different approach.
> >
> > Step 1: Start coding before you even try out a single bit on python
> > interpreter.
> > # myCode.py
> > import re
> > regex = re.compile(r'^b')
> > myList = ['foo', 'bar', 'baz']
> >
> > for item in myList:
> >   import pdb;pdb.set_trace()
> >
> > Step 2. Drop into pdb and then to IPython
> > Step 3. Try out your stuff *here*. You dont have to setup *myList*,
> *item,
> > regex *etc. You have everything ready waiting for you.
> > Step 4:
> > >> item
> > *'foo'*
> >
> > >> regex
> > *<_sre.SRE_Patten object at 0x123123>*
> >
> > >> regex.<TAB>
> > >> regex.mat<TAB>
> > >> regex.match?
> > *[read, find what it is, nope .. not what I wanted]*
> >
> > >> regex.<TAB>
> > >> regex.sea<TAB>
> > >> regex.search?
> > *[ah ha!]*
> >
> > >> regex.search(item)
> > >> Cntrl-D
> >
> > (pdb) c
> >
> > >> regex.search(item)
> > *<_sre.SRE_Match object at 0x123123>*
> >
> > *# phew, my re pattern works, awesome. I didnt have to setup dummy values
> > and then try it out etc.*
> > *# If re pattern didnt work the first time, I can make a new re patten
> and
> > try it out here. Again, I am not dealing with dummy values, but its the
> > actual values from the code -- foo, bar, baz (think if you're reading
> from
> > a
> > file, querying database etc.) work with real values, not dummy*
> >
> > *# Again, not knowing whether it is regex.search or regex.match to use
> > didnt
> > stop you from starting to code.*
> > *
> > *I call it breakpoint induced coding. Extremely helpful when you're
> > modifying someone else's code and you have no idea wht the heck all the
> > code
> > before this was doing. Insert a breakpoint (at the potential place you'd
> > edit/add code) and start from there.
> >
> > # someonesCode.py
> > import m1, m2, m3;
> >
> > call_function_1()
> > call_function_2()
> > do_extreme_stuff()
> > call_another_setof_functions()
> >
> > def do_extreme_stuff():
> >  s1
> >  s2
> >  potential_bug
> >  s3
> >
> >
> > Step 1.
> > s1
> > s2
> > *import pdb;pdb.set_trace()*
> > potential_bug
> > s3
> >
> > Step 2: pdb -> IPython
> > >> whos
> > * #see what the variables are, what's the status of the program right now
> > etc*
> >
> > >> try_a_much_better_approach()
> > >> make_sure_it_works_and_doesnt_break_anything()
> >
> > Step 3: Go back to text editor and put in your stuff there.
> > Step 4: Peace.
> >
> >
> > If you're still reading, hope I havent confused you.
> >
> >
> > Jeff
> > _______________________________________________
> > BangPypers mailing list
> > BangPypers at python.org
> > http://mail.python.org/mailman/listinfo/bangpypers
> >
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