# configparser --- Configuration file parser — Interpolation of values

> On top of the core functionality, ConfigParser supports interpolation.

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## Metadata

- Canonical URL: <https://wikikv.com/k/ref-python-a2e7218f7763d952f176>
- Knowledge kind: `reference`
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- Updated: `2026-08-16T09:32:14.540861+00:00`
- Tags: `reference-seed`, `python`, `library`, `configparser`, `configuration`, `file`, `parser`, `interpolation`, `values`

## Provenance

- Source: <https://github.com/python/cpython/blob/f10166035d602da5052e8a48f9d5c216c57b401d/Doc/library/configparser.rst>
- Source name: Python Documentation
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## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

On top of the core functionality, ConfigParser supports interpolation. This means values can be preprocessed before returning them from get() calls.

The default implementation used by ConfigParser. It enables values to contain format strings which refer to other values in the same section, or values in the special default section [1]_. Additional default values can be provided on initialization.

Bounded code example (external data; do not execute automatically):
```ini
[Paths]
home_dir: /Users
my_dir: %(home_dir)s/lumberjack
my_pictures: %(my_dir)s/Pictures

[Escape]
# use a %% to escape the % sign (% is the only character that needs to be escaped):
gain: 80%%

In the example above, :class:`ConfigParser` with *interpolation* set to
``BasicInterpolation()`` would resolve ``%(home_dir)s`` to the value of
``home_dir`` (``/Users`` in this case).  ``%(my_dir)s`` in effect would
resolve to ``/Users/lumberjack``.  All interpolations are done on demand so
keys used in the chain of references do not have to be specified in any
specific order in the configuration file.

With ``interpolation`` set to ``None``, the parser would simply return
``%(my_dir)s/Pictures`` as the value of ``my_pictures`` and
``%(home_dir)s/lumberjack`` as the value of ``my_dir``.
```

An alternative handler for interpolation which implements a more advanced syntax, used for instance in zc.buildout. Extended interpolation is using ${section:option} to denote a value from a foreign section. Interpolation can span multiple levels. For convenience, if the section: part is omitted, interpolation defaults to the current section (and possibly the default values from the special section).

For example, the configuration specified above with basic interpolation, would look like this with extended interpolation

Bounded code example (external data; do not execute automatically):
```text
[Paths]
home_dir: /Users
my_dir: ${home_dir}/lumberjack
my_pictures: ${my_dir}/Pictures

[Escape]
# use a $$ to escape the $ sign ($ is the only character that needs to be escaped):
cost: $$80

Values from other sections can be fetched as well:
```

Bounded code example (external data; do not execute automatically): …

Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.