debugging.md

Debugging Python Code

• Try and Else Block
• Pdb
• set trace method

Common Python Errors

• SyntaxError
• NameError This usually occurs when a variable is not defined or it hasn't been assigned yet.
• TypeError This usually occurs when an operation or function is applied to a wrong type.
• IndexError This occurs when we are trying to access an element in a list using invalid index.
• ValueError This occurs when a built in operation or function receives an arguement that has the right type but an inappropiate value
• KeyError This occurs when a dictionary doesn't have a specific key.
• AttributeError This occurs when a variable doesn't have an attribute.

Raising Our own Exceptions

• We can raise our own error exceptions

raise ValueError('invalid Error')

• Lets say we have a simple function and we want it to have our own exception.

def color(text,color):
    if type(text) is not str:
        raise TypeError('Enter a valid String')
    print(f'This {text} is using {color}.')

Handling Errors

• In python we can handle errors using try and except

try:
    x
except ValueError:
    print("there's a error")

Else and Finally. Finally would run no matter what.

# a small program
try:
    x = int(input("Enter a number"))
except:
    print("Enter a valid Number")
else:
    print("Thanks for a valid number")
finally:
    print("I will run no matter what hehehe")

Debugging our code using PDB

• In order to set a breakpoint we use pdb.set_trace()
• After setting a breakpoint then we can go line by line through our code.

Common PDB commands

• l List
• n next line
• p print
• c continue