Working with the Python Debugger

Python Debugger may be a new word for the beginner developers . In this post , we will try to explain the meaning of Debugging and Debugging with Python . 

What is Debugging? 

Debugging means the complete control over the program execution. Developers use debugging to overcome program from any bad issues. So debugging is a healthier process for the program and keeps the diseases bugs far away. Python also allows developers to debug the programs using pdb module that comes with standard Python by default. We just need to import pdb module in the Python script. Using pdb module, we can set breakpoints in the program to check the current status. We can Change the flow of execution by using  jump,  continue statements . Let’s understand debugging with a Python program.

Example:

Python3

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# Program to print Multiplication 
# table of a Number
n=5
for x in range(1,11) :
  print( n , '*' , x , '=' , n*x )

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Output:

5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25
5 * 6 = 30
5 * 7 = 35
5 * 8 = 40
5 * 9 = 45
5 * 10 = 50

This program simply print multiplication table but now we need to debug the loop steps using set_trace() function call to pdb module .



Example:

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# Python Program to print Multiplication Table
# We want to debug the for loop so we use
# set_trace() call to pdb module
  
import pdb
  
  
# It means , the Start of Debugging Mode
pdb.set_trace()
  
n=5
for x in range(1,11) :
  print( n , '*' , x , '=' , n*x )

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Output:

Basic Commands to use Python Debugger 

 list command to see entire program .

list command in pdb debugger

list command

 list 3 , 6  to see the program lines from 3 to 5 only .

list command in pdb debugger

list lines command in pdb debugger

 

 break command to stop the program execution at particular line .

break command in pdb debugger

 continue command to see the next step in the loop .

continue command in pdb debugger

continue command in pdb debugger

jump command allows us to go on any particular line in the program .

jump command in pdb debugger

jump command in pdb debugger

 pp command to see variable value at the current position in the program .

pp command in pdb debugger

pp command in pdb debugger

disable command to disable the current line output and we can use continue command to skip this line in program. We use  quit or  exit command to come outside the debugging mode .

Conclusion 

Debugging helps developers to analyze programs line by line. Developers see the every interpreted line by using debugging mode in programs. Python comes with by default debugger that is easy to import and use. So it is good to start with debugger when confused about execution of large loops, current variable values and all . 




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