Slides from the training on the topic "Python Programming Essentials"

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Talent brewed by the industry itself
pdb – The interactive Debugger
Pavan Verma
@YinYangPavan
Founder, P3 InfoTech Solutions Pvt. Ltd.
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Python Programming Essentials

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Content
 Python debugger introduction
 Enter into debugger via command line
 pdb commands
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PDB - The Python Debugger
1. pdb implements an interactive debugging
environment for Python programs
2. It lest you do a the following :
1. Pause your program
2. Look at the values of variables
3. Program execution step-by-step
4. Step up and down the call stack
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Enter into Debugger via command line
python –m pdb filename
Running the debugger from the command line causes it to
load your source file and stop execution on the first
statement it finds
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Enter into Debugger from within program (1)
import pdb
pdb.set_trace()
Use pdb.set_trace()in the program where
ever you want the program to enter into the
debugger
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pdb commands
list or l
Using list with a single
numerical argument lists 11
lines around that line
instead of the current line
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pdb commands (2)
where
At any point while the
debugger is running
you can use where
(abbreviated w) to find
out exactly what line is
being executed and
where on the call stack
you are
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pdb commands (3)
step
Use step to execute the
current line and then stop
at the next execution
point – either the first
statement inside a
function being called or
the next line of the
current function
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pdb commands (4)
next or n:
The next command is like
step, but does not enter
functions called from the
statement being executed. In
effect, it steps all the way
through the function call to
the next statement in the
current function in a single
operation.
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pdb commands (5)
up (u) and down (d)
• Move between frames
within the current call stack
using up and down
• up (abbreviated u) moves
towards older frames on
the stack
• down (abbreviated d)
moves towards newer
frames
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Resources
 http://docs.python.org/2/library/pdb.html
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