A brief introduction python's handy built-in debugger, Pdb. Presented as a part of the Hackbright Academy summer fellowship.

1. Debugging
Python with Pdb
Noelle Daley, 7.13.2015

2. Debugging
numbers = [1, 2, 3, 4, 10, -4, -7, 0]
def all_even(l):
even_numbers = []
for number in l:
if number / 2 == 0:
even_numbers.extend(number)
return even_numbers
all_even(numbers)

3. One option: all the print statements!
for number in l:
print "Number is: ", number
if number / 2 == 0:
print number, " is an even number!"
even_numbers.extend(number)
print "List now includes:"
print even_numbers

4. Enter Pdb!
Pdb is the built-in Python
debugger.
It helps you debug programs
interactively, allowing you to
step into functions, test
variables, and much more.
*not really

5. Using Pdb
Import pdb, then insert where you’d like to start
debugging:
numbers = [1, 2, 3, 4, 10, -4, -7, 0]
import pdb; pdb.set_trace()
def all_even(l):
even_numbers = []...

6. Using Pdb

7. Pdb Commands
l (list) -- shows where you are in your script
n (next) -- steps to next line of execution (but not into functions!)
s (step) -- steps into next line of execution, including functions
r (return) -- steps to the end of currently executing function
c (continue) -- executes code
q (quit) -- exit the debugger
? (help) -- shows all commands

8. Pbd Commands: l
List where you are in the script:

9. Pbd Commands: n
Step to next line of execution:

10. Pbd Commands: s
Step into next line of execution:

11. Evaluating Variables!!!!!!!!!!
1 / 2 == 0?!

12. Recap
Pdb is awesome!
Use it when print statements are
cluttering your script.
Import: import pdb; pdb.set_trace()
Navigate with l, n, and s.

13. Resources
● Debugging in Python - Python Conquers the Universe
● Python Docs - the Python Debugger
● Tutorial: Debugging Python apps with Pdb