Splitting and Joining Strings

15 min · Beginner

Converting between a single formatted string and a list of tokens is a daily task in backend development. Python provides split() and join() for seamless conversions.

Splitting strings with split()

split() is a string method that cuts a string into a list of smaller strings. With no argument it cuts on any run of whitespace and drops the empty pieces.

By default, .split() breaks a string on any whitespace (spaces, tabs, newlines), discarding consecutive spaces.

Python

sentence = "FastAPI  PostgreSQL  Docker"tags = sentence.split()print(tags)

split and join are opposites. split(",") cuts the string "red,green,blue" into a list of three strings: red, green and blue. "-".join(items) glues those three strings back into one string, "red-green-blue", with a hyphen between each pair.

Example 1 · Counting the words in a review

Python

review = "fast delivery and great support"words = review.split()print(words)print(len(words))

Output

['fast', 'delivery', 'and', 'great', 'support']
5

What this code does

split() cuts the sentence on spaces and returns a list.
len of the list is the number of words.

The output is ['FastAPI', 'PostgreSQL', 'Docker'].

Custom delimiters: parsing CSV

Delimiter is the character or text that separates the parts of a string, such as a comma in a CSV line. Pass it to split(delimiter) to cut there.

Pass a specific delimiter to .split(delimiter) to parse structured data like CSV lines.

Python

record = "101,Aarav,Software Engineer,Bengaluru"fields = record.split(",")print(fields[1])print(fields[3])

Example 2 · Reading one CSV row

Python

row = "A102,Laptop,2,45000"fields = row.split(",")total = int(fields[2]) * int(fields[3])print(fields[1])print(f"{fields[0]}: {total}")

Output

Laptop
A102: 90000

What this code does

Splitting on a comma gives four text fields.
The quantity and price are text, so int turns them into numbers before multiplying.
The f-string builds the final line.

Extracts 'Aarav' and 'Bengaluru' cleanly by splitting on commas.

Joining lists with join()

join() is a string method that glues the items of a list of strings into one string. It is called on the separator: ", ".join(items).

To combine an iterable of strings into one text, call .join() on the separator string: separator.join(list).

Python

words = ["Python", "is", "awesome"]sentence = " ".join(words)print(sentence)

Example 3 · Building a bulleted report

Python

skills = ["FastAPI", "SQLAlchemy", "Pydantic", "pytest"]# Create a clean bulleted reportreport = "\n- ".join(skills)print("- " + report)

Output

- FastAPI
- SQLAlchemy
- Pydantic
- pytest

What this code does

Joins skills with newline and bullet dash \n- .
Outputs each skill on a neat bulleted line.

The console displays Python is awesome. Using ", ".join(items) formats lists into clean comma-separated text.

Next step

Check your understanding

9 quick questions

Splitting and Joining Strings

15 min · Beginner

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Converting between a single formatted string and a list of tokens is a daily task in backend development. Python provides split() and join() for seamless conversions.

Splitting strings with split()

split() is a string method that cuts a string into a list of smaller strings. With no argument it cuts on any run of whitespace and drops the empty pieces.

By default, .split() breaks a string on any whitespace (spaces, tabs, newlines), discarding consecutive spaces.

Python

sentence = "FastAPI  PostgreSQL  Docker"tags = sentence.split()print(tags)

Example 1 · Counting the words in a review

Python

review = "fast delivery and great support"words = review.split()print(words)print(len(words))

Output

['fast', 'delivery', 'and', 'great', 'support']
5

What this code does

split() cuts the sentence on spaces and returns a list.
len of the list is the number of words.

The output is ['FastAPI', 'PostgreSQL', 'Docker'].

Custom delimiters: parsing CSV

Delimiter is the character or text that separates the parts of a string, such as a comma in a CSV line. Pass it to split(delimiter) to cut there.

Pass a specific delimiter to .split(delimiter) to parse structured data like CSV lines.

Python

record = "101,Aarav,Software Engineer,Bengaluru"fields = record.split(",")print(fields[1])print(fields[3])

Example 2 · Reading one CSV row

Python

row = "A102,Laptop,2,45000"fields = row.split(",")total = int(fields[2]) * int(fields[3])print(fields[1])print(f"{fields[0]}: {total}")

Output

Laptop
A102: 90000

What this code does

Splitting on a comma gives four text fields.
The quantity and price are text, so int turns them into numbers before multiplying.
The f-string builds the final line.

Extracts 'Aarav' and 'Bengaluru' cleanly by splitting on commas.

Joining lists with join()

join() is a string method that glues the items of a list of strings into one string. It is called on the separator: ", ".join(items).

To combine an iterable of strings into one text, call .join() on the separator string: separator.join(list).

Python

words = ["Python", "is", "awesome"]sentence = " ".join(words)print(sentence)

Example 3 · Building a bulleted report

Python

skills = ["FastAPI", "SQLAlchemy", "Pydantic", "pytest"]# Create a clean bulleted reportreport = "\n- ".join(skills)print("- " + report)

Output

- FastAPI
- SQLAlchemy
- Pydantic
- pytest

What this code does

Joins skills with newline and bullet dash \n- .
Outputs each skill on a neat bulleted line.

The console displays Python is awesome. Using ", ".join(items) formats lists into clean comma-separated text.

Next step

Check your understanding

9 quick questions