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Python Pandas Error tokenizing data

python
error-handling
csv-module
pandas-read-csv
Alex KataevbyAlex Kataev·Aug 27, 2024
TLDR

Problem: Pandas Error tokenizing data. Solution: Pandas read_csv function with on_bad_lines parameter. For Pandas ≥ 1.3.0, use either skip to bypass erroneous lines or warn to receive alerts:

# Nothing slips past pandas on our watch! df = pd.read_csv('file.csv', on_bad_lines='skip')

Suspect funny business with the delimiter character? Define it explicitly:

# Tabs everywhere? Say no more! df = pd.read_csv('file.csv', sep='\t')

Dodgy leading or trailing whitespaces in your data? Include skipinitialspace=True:

# Pandas sure doesn't like spaces before coffee (or data) df = pd.read_csv('file.csv', skipinitialspace=True)

Diagnosing CSV's quirky ways

Tackling CSV compatibility issues requires a diagnosis before treatment. Potential ailments include:

  • Mismatched column count
  • Inconsistent header rows
  • Unforeseen delimiter character
  • Misleading/non-representative header rows

Employ csv.Sniffer() for a clue or inspect the CSV's initial lines. Ensure you're starting your read from the first line post-diagnosis.

When headers play hooky, specify column names with the names parameter. Check the alignment between your names list and the CSV's actual column count to avoid mismatch tantrums!

When pandas need a hand with error handling

For decidedly eccentric CSVs, more bespoke handling of "problematic" lines might be warranted:

def handle_bad_lines(err): # Log, fix or dismiss errors here as you see fit, like a data superhero pass df = pd.read_csv('file.csv', on_bad_lines=handle_bad_lines)

This lets you log, overlook, or even correct lines in situ for a more tailored data processing.

Easier understanding with visualization

To help you grasp the "Error tokenizing data" concept, let's take a visual ride:

Our Closet Items: [👕, 👚, 🩳, 'sock', '🧦', 2️⃣4️⃣, 🧥]

How our pandas.read_csv() behaves is akin to a neat freak arranging a wardrobe with a particular arrangement in mind:

Expected Format (or where they think they belong): [Clothing Type, Size, Color]

Unformatted or unexpected items attract pandas' ire:

💼➡️🧹💥: ['Mismatch!', 'Could not parse!', 'Error tokenizing']

An unhappy pandas (organizer) might throw an error encountering unexpected items (data):

🚫 ('sock', 2️⃣4️⃣) 🚫 - Clothes not sticking to the dress code!

Ensure your data (or clothes) adheres to the expected format before inviting pandas (the neat freak) over!

Hitting a wall with pandas? Try Python's csv module

When pandas read_csv appears to be a hammer unable to hit the nail, the Python csv module might have the chisel for your needs. It lets you craft custom CSV reading strategies, particularly useful when pandas seems like an overkill!