Format method

As explained in Python Workout: 50 ten-minute exercises

str.format is a Python string method that produces formatted text by substituting values into replacement fields.

When output combines values of different types or must fit fixed columns, str.format substitutes arguments into numbered replacement fields such as {0}, {1}, and {2}. section 3.22 section 1.6

The method becomes especially useful when formatting structured output:

• Unpack a tuple into separate format arguments with format(*person). section 3.22
• Add a colon and format specification inside a field, as in {1:10}, to create a padded ten-character column. section 3.22
• Format floating-point values with controlled precision, width, alignment, and padding. section 3.22

A minimal substitution

Use 'Hello, {0}'.format('world') to place a value into a replacement field. The same task can use an f-string, but str.format remains useful when arguments are supplied separately. section 1.6

Figure 3.11 Iterating over our list of tuples (from the Python Tutor)

Trace tuple iteration while formatted values are prepared for aligned output. section 3.22

How Python Workout: 50 ten-minute exercises covers it

How deep it goes

Explains positional fields, tuple unpacking, widths, alignment, padding, and floating-point precision.

Examples

Uses a guessed number, Hello world, and sorted people tuples with aligned travel-time columns.

What it assumes

Assumes familiarity with tuples, iteration, function arguments, and basic string output.

What you can do after

Apply it via Python's str.format method to substitute values and produce controlled text layouts.

How it connects

Connects string formatting with tuples, argument unpacking, f-strings, and numeric formatting.

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Also explained in

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  100 Java Mistakes and How to Avoid ThemString.format is a Java API method that returns a formatted string constructed from a format string and supplied arguments.

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Related concepts

• f-stringalternative to · An f-string is a Python formatted string literal that evaluates embedded expressions and inserts their formatted values into the resulting string.
• format stringuses · A format string is a character sequence containing literal text and directives that specify how supplied values are represented in formatted input or output.
• fmtalternative to · fmt is a software library or package that provides formatted text generation and, in some implementations, formatted input and output operations.
• timestampused by · A timestamp is a value representing a specific point in time, typically associated with an event, observation, or data item.
• __str__part of · __str__ is a Python special method that returns an object's informal, human-readable string representation.

This explainer was generated by Manning's knowledge graph from the text of Python Workout: 50 ten-minute exercises. The section links point to the parts of the book it draws on.