Add a prefix to selected lines of a multiline string.
How It Works
textwrap.indent(text, prefix, predicate=None) inserts a prefix at the start of lines chosen by a predicate. By default blank lines are not prefixed.
Step-by-Step Example
import textwrap
indented_text = textwrap.indent('alpha\nbeta\n', '> ')
print(indented_text.splitlines())Understanding the Example
- The expression "textwrap.indent('alpha\\nbeta\\n', '> ')" supplies the value stored as 'indented_text'. This value is then used or checked by the later statements.
- The print() call exposes the result so you can compare it with the behavior described above. Check the value and its type when experimenting.
A successful run of this example prints the following output:
['> alpha', '> beta']Where This Fits in a Real Program
Start by writing down examples that should match and examples that must fail. Check whether you need to locate a substring, match a prefix or validate an entire field; these are different operations. Unicode and escape sequences can also change which characters are matched, so test accented text and empty input.
Practice: Try It Yourself
Provide a predicate to control which lines are prefixed.
For this exercise, predict the result before running the changed code. Then explain the difference between the original and modified cases using the actual values, not just whether the program completed.
Further Reading
Read the official Python documentation for complete parameters, return types and exceptions.
Common Beginner Mistakes
- Assuming blank lines are prefixed automatically or that indent changes the original string.
- Quote a multiline comment using a four-space prefix.
Key Takeaways
- Add a prefix to selected lines of a multiline string.
- textwrap.indent(text, prefix, predicate=None) inserts a prefix at the start of lines chosen by a predicate.
- Apply the demonstrated operation to the practice input and verify its result before depending on it in a larger program.