str.len() for string length in Pandas - Step-by-Step Execution

Concept Flow - str.len() for string length

Start with a pandas Series of strings

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Call str.len() method

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Calculate length of each string

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Return Series of lengths

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Use or display result

We start with a pandas Series containing strings. Using str.len(), pandas calculates the length of each string and returns a new Series with these lengths.

Execution Sample

Pandas

import pandas as pd
s = pd.Series(['apple', 'banana', 'cherry'])
lengths = s.str.len()
print(lengths)

This code creates a Series of fruits and calculates the length of each fruit name.

Execution Table

Step	Input String	Action	Length Calculated	Output Series Value
1	'apple'	Calculate length	5	5
2	'banana'	Calculate length	6	6
3	'cherry'	Calculate length	6	6
4	All strings processed	Return Series	-	[5, 6, 6]

💡 All strings processed, lengths returned as a Series.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
s	['apple', 'banana', 'cherry']	same	same	same	same
lengths	empty	5	5, 6	5, 6, 6	[5, 6, 6]

Key Moments - 2 Insights

Why does str.len() return a Series and not a single number?

Because str.len() calculates the length of each string in the Series individually, it returns a Series of lengths, one for each original string, as shown in execution_table rows 1-4.

What happens if the Series contains a missing value (NaN)?

If the Series has NaN, str.len() returns NaN for that position. This is because length cannot be calculated for missing values, similar to how execution_table shows lengths only for valid strings.

Visual Quiz - 3 Questions

Look at the execution_table, what is the length calculated for the string 'banana'?

A 6

B 5

C 7

D 4

💡 Hint

Check execution_table row 2 under 'Length Calculated' column.

At which step does the method return the full Series of lengths?

A Step 3

B Step 2

C Step 4

D Step 1

💡 Hint

Look at the 'Action' column in execution_table for when all strings are processed.

If the input Series had an empty string '', what would str.len() return for that entry?

A NaN

B 0

C 1

D Error

💡 Hint

Recall that length counts characters; empty string has zero characters.

Concept Snapshot

pandas Series.str.len()
- Calculates length of each string in a Series
- Returns a Series of integer lengths
- Handles missing values by returning NaN
- Useful for quick string length analysis

Full Transcript

This visual execution shows how pandas Series.str.len() works. We start with a Series of strings. Each string's length is calculated one by one. The lengths are collected into a new Series. The method returns this Series of lengths. If a string is missing, the length is NaN. This helps analyze string sizes easily in data science tasks.