Asp Forum - About reading Python code

toolmaster

3/17/2008 3:54:00 AM

Hello. I wonder what's the effective way of figuring out how a piece
of python code works. With C I often find it very useful to be able to
run the code in step mode and set breakpoints in a debugger so I can
watch how the it executes, how the data change and how the code jumps
from one function to another. But with Python, the debugger is a
little primitive. The default IDLE doesn't even allow me to set a
breakpoint. When the code is long, I am often lost in it.

So I'm curious how to read code effectively. I agree that python code
is clear, but when it becomes long, reading it can still be a hard
work.

8 Answers

toolmaster

3/17/2008 3:57:00 AM

On Mar 17, 11:54 am, WaterWalk <toolmas...@163.com> wrote:
> Hello. I wonder what's the effective way of figuring out how a piece
> of python code works. With C I often find it very useful to be able to
> run the code in step mode and set breakpoints in a debugger so I can
> watch how the it executes, how the data change and how the code jumps
> from one function to another. But with Python, the debugger is a
> little primitive. The default IDLE doesn't even allow me to set a
> breakpoint. When the code is long, I am often lost in it.
>
> So I'm curious how to read code effectively. I agree that python code
> is clear, but when it becomes long, reading it can still be a hard
> work.

BTW. I think this problem also exists in other script languages.

Stargaming

3/17/2008 5:55:00 AM

On Sun, 16 Mar 2008 20:54:01 -0700, WaterWalk wrote:

> Hello. I wonder what's the effective way of figuring out how a piece of
> python code works.

If your Python code is well-written, it should be easy figuring out what
it means by just reading it. For more complex programs, of course, this
method can fail.

> With C I often find it very useful to be able to run
> the code in step mode and set breakpoints in a debugger so I can watch
> how the it executes, how the data change and how the code jumps from one
> function to another. But with Python, the debugger is a little
> primitive. The default IDLE doesn't even allow me to set a breakpoint.
> When the code is long, I am often lost in it.

IDLE is just, well, a batteries-included editor. There are many people
(me included) who do *not* like it because it's so weak and doesn't have
any real uses cases if your programs get sufficiently complex (because
IDLE itself is sufficiently primitive).

You might be interested in *real* debuggers, such as the Python Debugger
`PDB <http://docs.pytho...module-pd...`_. If you don't find
its usage obvious, a quick google search just turned up a nice `tutorial
<http://www.ferg.org/papers/debugging_in_pytho...`_.

You might find the `Python Profilers <http://docs.pytho...
profile.html>`_ particularly interesting, `profile` for finding out which
function sucks up the most calls/time, `trace` for more sophisticated
stuff.
`pythontracer <http://code.google.com/p/pythont...` sounds like a
good combination of both.

> So I'm curious how to read code effectively. I agree that python code is
> clear, but when it becomes long, reading it can still be a hard work.

A common practice is just inserting `print` statements since it's so
easy. If you think your debugging isn't temporary but could be useful and
will be enabled every now and then, you could also use the `logging
module <http://docs.pytho...module-logging.html>`_ with the
``DEBUG`` level.

There was a blog post recently about how to do this `generically for
functions <http://wordaligned.org/article...`_.

> BTW. I think this problem also exists in other script languages.

FWIW, I think it's particularly easier in scripting languages to
implement all kinds of tracing (apart from debugging, which is rather
unpopular in Python) because you have one *extra* level (the interpreter)
between your machine and your code.

HTH,
Stargaming

toolmaster

3/17/2008 8:13:00 AM

On Mar 17, 1:54 pm, Stargaming <stargam...@gmail.com> wrote:
> On Sun, 16 Mar 2008 20:54:01 -0700, WaterWalk wrote:
> > Hello. I wonder what's the effective way of figuring out how a piece of
> > python code works.
>
> If your Python code is well-written, it should be easy figuring out what
> it means by just reading it. For more complex programs, of course, this
> method can fail.
>
> > With C I often find it very useful to be able to run
> > the code in step mode and set breakpoints in a debugger so I can watch
> > how the it executes, how the data change and how the code jumps from one
> > function to another. But with Python, the debugger is a little
> > primitive. The default IDLE doesn't even allow me to set a breakpoint.
> > When the code is long, I am often lost in it.
>
> IDLE is just, well, a batteries-included editor. There are many people
> (me included) who do *not* like it because it's so weak and doesn't have
> any real uses cases if your programs get sufficiently complex (because
> IDLE itself is sufficiently primitive).
>
> You might be interested in *real* debuggers, such as the Python Debugger
> `PDB <http://docs.pytho...module-pd...`_. If you don't find
> its usage obvious, a quick google search just turned up a nice `tutorial
> <http://www.ferg.org/papers/debugging_in_pytho...`_.
>
> You might find the `Python Profilers <http://docs.pytho...
> profile.html>`_ particularly interesting, `profile` for finding out which
> function sucks up the most calls/time, `trace` for more sophisticated
> stuff.
> `pythontracer <http://code.google.com/p/pythont...` sounds like a
> good combination of both.
>
> > So I'm curious how to read code effectively. I agree that python code is
> > clear, but when it becomes long, reading it can still be a hard work.
>
> A common practice is just inserting `print` statements since it's so
> easy. If you think your debugging isn't temporary but could be useful and
> will be enabled every now and then, you could also use the `logging
> module <http://docs.pytho...module-logging.html>`_ with the
> ``DEBUG`` level.
>
> There was a blog post recently about how to do this `generically for
> functions <http://wordaligned.org/article...`_.
>
> > BTW. I think this problem also exists in other script languages.
>
> FWIW, I think it's particularly easier in scripting languages to
> implement all kinds of tracing (apart from debugging, which is rather
> unpopular in Python) because you have one *extra* level (the interpreter)
> between your machine and your code.
>
> HTH,
> Stargaming

Thanks for your informative reply. I'll try them. I think I need more
practice to familiarize myself with those idioms of Python.

Ben C

3/17/2008 8:49:00 AM

On 2008-03-17, WaterWalk <toolmaster@163.com> wrote:
> Hello. I wonder what's the effective way of figuring out how a piece
> of python code works. With C I often find it very useful to be able to
> run the code in step mode and set breakpoints in a debugger so I can
> watch how the it executes, how the data change and how the code jumps
> from one function to another. But with Python, the debugger is a
> little primitive. The default IDLE doesn't even allow me to set a
> breakpoint.

It does, you just right-click and go "set breakpoint". But yes IDLE is a
bit basic.

nir1408

3/17/2008 9:55:00 AM

On Mar 17, 5:54 am, WaterWalk <toolmas...@163.com> wrote:
> Hello. I wonder what's the effective way of figuring out how a piece
> ofpythoncode works. With C I often find it very useful to be able to
> run the code in step mode and set breakpoints in adebuggerso I can
> watch how the it executes, how the data change and how the code jumps
> from one function to another. But withPython, thedebuggeris a
> little primitive. The default IDLE doesn't even allow me to set a
> breakpoint. When the code is long, I am often lost in it.
>
> So I'm curious how to read code effectively. I agree thatpythoncode
> is clear, but when it becomes long, reading it can still be a hard
> work.

Try Winpdb - www.winpdb.org (works on Linux as well). Don't forget to
send feedback.

Roman Dodin

3/17/2008 10:12:00 AM

WaterWalk Ð¿Ð¸Ñ?ÐµÑ?:
> Hello. I wonder what's the effective way of figuring out how a piece
> of python code works. With C I often find it very useful to be able to
> run the code in step mode and set breakpoints in a debugger so I can
> watch how the it executes, how the data change and how the code jumps
> from one function to another. But with Python, the debugger is a
> little primitive. The default IDLE doesn't even allow me to set a
> breakpoint. When the code is long, I am often lost in it.
>
> So I'm curious how to read code effectively. I agree that python code
> is clear, but when it becomes long, reading it can still be a hard
> work.
>

You also can use free IDE (for example Eclipse) and PyDev plugin, which
includes comfortable Debugger

james.pablos

12/2/2011 12:11:00 PM

On Nov 30, 11:24 am, band beyond description
<everybody's.d...@that.rag.com> wrote:

> and apologies to folks with cancer, but Cain's not so far out of the
> woods from his own complicated battle with the disease that, even if he
> didn't have that laundry list of decrepitude you list above, some might
> consider that health issue alone a disqualification.

"my wife did not know I was sending that woman money every month"

That shit would not fly in the Pablos house. No sireeeee...

Dave Kelly

12/2/2011 4:31:00 PM

"James Pablum" <james.pablos@gmail.com> wrote in message

> That shit would not fly in the Pablos house. No sireeeee...

Your monthly "gift" to the pool boy doesn't count...uh...right?
Thought not.

comp.lang.python

About reading Python code

toolmaster

toolmaster

Stargaming

toolmaster

Ben C

nir1408

Roman Dodin

james.pablos

Dave Kelly

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