CommaSeparatedListOutputParser in LangChain - Step-by-Step Execution

Concept Flow - CommaSeparatedListOutputParser

Receive raw text output

↓

Split text by commas

↓

Trim whitespace from each item

↓

Return list of clean strings

The parser takes a string with comma-separated values, splits it by commas, trims spaces, and returns a list of clean items.

Execution Sample

LangChain

from langchain.output_parsers import CommaSeparatedListOutputParser
parser = CommaSeparatedListOutputParser()
text = 'apple, banana, cherry'
result = parser.parse(text)
print(result)

This code parses a comma-separated string into a list of trimmed strings.

Execution Table

Step	Action	Input	Output	Notes
1	Receive raw text	'apple, banana, cherry'	'apple, banana, cherry'	Initial input string
2	Split by commas	'apple, banana, cherry'	['apple', ' banana', ' cherry']	Split into list with spaces
3	Trim whitespace	['apple', ' banana', ' cherry']	['apple', 'banana', 'cherry']	Remove spaces around items
4	Return list	['apple', 'banana', 'cherry']	['apple', 'banana', 'cherry']	Final parsed list

💡 Parsing completes after trimming and returning the list of items.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
text	'apple, banana, cherry'	'apple, banana, cherry'	'apple, banana, cherry'	'apple, banana, cherry'
split_list	N/A	['apple', ' banana', ' cherry']	['apple', 'banana', 'cherry']	['apple', 'banana', 'cherry']
result	N/A	N/A	['apple', 'banana', 'cherry']	['apple', 'banana', 'cherry']

Key Moments - 3 Insights

Why do some items have spaces before trimming?

After splitting by commas (Step 2), spaces remain because split only separates by commas, not spaces. Trimming in Step 3 removes these spaces.

What happens if the input string has no commas?

The split returns a list with one item (the whole string). Then trimming applies but the list stays single-item, as shown in Step 2 and 3.

Can the parser handle empty strings between commas?

Yes, splitting 'a,,b' results in ['a', '', 'b']. The empty string remains after trimming, so the list includes empty items.

Visual Quiz - 3 Questions

Look at the execution table, what is the output after Step 2?

A ['apple banana cherry']

B ['apple', ' banana', ' cherry']

C ['apple', 'banana', 'cherry']

D ['apple', 'banana cherry']

💡 Hint

Check the 'Output' column for Step 2 in the execution_table.

At which step are spaces removed from each list item?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Action' column describing trimming whitespace.

If the input is 'dog,cat', what will the final list be?

A ['dog cat']

B ['dog,cat']

C ['dog', 'cat']

D ['dog', '', 'cat']

💡 Hint

Refer to how splitting and trimming works in the variable_tracker and execution_table.

Concept Snapshot

CommaSeparatedListOutputParser:
- Input: string with commas
- Splits string by commas
- Trims spaces from each item
- Returns list of clean strings
- Handles empty items if present

Full Transcript

The CommaSeparatedListOutputParser takes a string of items separated by commas. It splits the string at each comma, creating a list of items. Each item may have spaces around it, so the parser trims these spaces. Finally, it returns a list of clean strings without extra spaces. This process helps convert raw text output into a structured list for easier use in programs.