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Errors

Updated Oct 31, 2019 ·

Overview​

An error occurs when code violates a rule, causing the program to stop. Errors are also called exceptions, and they prevent code from running. To avoid errors, it's important to write clean and valid code.

Common Errors​

TypeError​

Occurs when incompatible data types are used together.

Example: Adding a string to an integer.

print("Hello" + 10)

Output:

`TypeError: can only concatenate str (not "int") to str`

ValueError​

Happens when a value is outside the expected range or type.

Example: Trying to convert a non-numeric string to an integer.

print(int("Hello"))

Output:

`ValueError: invalid literal for int() with base 10: 'Hello'`

Tracebacks​

A traceback is a report that shows what type of error occurred and where in the code it happened. The traceback details shows error type, file, and line number where the issue occurred.

Example: Converting an invalid string to a number.

float("Hello")

Output:

Traceback (most recent call last):
  File "script.py", line 1, in <module>
    float("Hello")
ValueError: could not convert string to float: 'Hello'

Errors from Packages​

Errors can also occur when using code from external packages like pandas. You won’t see the code running behind the scenes, but it still executes.

Tracebacks from Packages​

Tracebacks from packages show where the error occurred in their source code.

Example: Accessing a non-existent column in a DataFrame.

import pandas as pd
df = pd.DataFrame({"name": ["John", "Jane"]})
print(df["tag"])

Output:

Traceback (most recent call last):
  File "script.py", line 3, in <module>
    print(df["tag"])
KeyError: 'tag'

The traceback shows the location of the error in the package's source code (e.g., script.py).

  • It will highlight the line in your code where the error happened.
  • The error message (like KeyError) indicates the problem, such as accessing a non-existent key.