How to Format Strings with Named Placeholders in Python

Format a template string using named placeholders with the str.format() method and a dictionary.

Easy Python 3.6+ Aug 9, 2026 Strings & text 15 views 0 copies

string format placeholders f-string

Python code

10 lines

Python 3.6+

def format_named(template, data):
    """Format a template string using named placeholders."""
    return template.format(**data)


if __name__ == "__main__":
    template = "Hello {name}, you are {age} years old and live in {city}."
    data = {"name": "Alice", "age": 30, "city": "London"}
    result = format_named(template, data)
    print(result)

Output

stdout

Hello Alice, you are 30 years old and live in London.

How it works

The str.format() method supports named placeholders by using {name} inside the template. By unpacking the dictionary with **data, each key becomes a keyword argument to format(), which replaces the placeholders with corresponding values. This approach keeps the template readable and decouples the data from the formatting logic. It's safe as long as all placeholders exist in the dictionary; otherwise, a KeyError is raised. The method is part of the standard library, so no external packages are needed.

Common mistakes

Forgetting to use `**` when passing the dictionary, causing a TypeError
Not accounting for missing keys, which raises KeyError
Using uppercase `Format` instead of `format`
Mixing positional and named placeholders in a confusing way

Variations

Use f-strings with manual dictionary access: `f"Hello {data['name']}"`
Use `string.Template` with `$placeholder` syntax for simpler substitution

Real-world use cases

Generating personalized email content from user profile data dictionaries.
Building SQL query strings with safe parameter substitution for logging or templates.
Producing configuration-based report templates where field names vary per client.

How to Format Strings with Named Placeholders in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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Python code

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How it works

Common mistakes

Variations

Real-world use cases

More from Strings & text

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