Introduction to errors

Intermediate Python for Developers

Jasmin Ludolf

Senior Data Science Content Developer

What is an error?

Code that violates a rule
Error = Exception
Cause our program to terminate!

Hierarchy of some Python exceptions

¹ https://docs.python.org/3/library/exceptions.html#exception-hierarchy

TypeError

Incompatible data type

"Hello" + 5

TypeError output showing strings and integers cannot be combined

ValueError

float("Hello")

ValueError output confirming that the string 'Hello' cannot be converred to a float

The value is not within an acceptable range

float("2")

Output showing the result 2.0 without an error

Tracebacks

Traceback message

Tracebacks

Traceback message highlighting the error type

Tracebacks

Traceback message highlight the code that caused the error

Code in packages

Packages contain other people's code, e.g., custom functions
Known as source code
pip install <package> downloads source code to our local environment
The pandas' pd.read_csv() function executes the code written for that custom function behind the scenes

Tracebacks from packages

# Import pandas package
import pandas as pd

# Create pandas DataFrame                 
products = pd.DataFrame({"ID": "ABC1",
                         "price": 29.99})

# Try to access the non-existent "tag" column
products["tag"]