ZConfig.substitution — String substitution

Shell-style string substitution helper.

This module provides a basic substitution facility similar to that found in the Bourne shell (sh on most UNIX platforms).

The replacements supported by this module include:

Source Replacement Notes
$$ $
$name The result of looking up name
${name} The result of looking up name  


  1. This is different from the Bourne shell, which uses \$ to generate a $ in the result text. This difference avoids having as many special characters in the syntax.
  2. Any character which immediately follows name may not be a valid character in a name.

In each case, name is a non-empty sequence of alphanumeric and underscore characters not starting with a digit. If there is not a replacement for name, the exception SubstitutionReplacementError is raised. Note that the lookup is expected to be case-insensitive; this module will always use a lower-case version of the name to perform the query.

This module provides these functions:

ZConfig.substitution.substitute(s, mapping)

Substitute values from mapping into s.

mapping can be a dict or any type that supports the get() method of the mapping protocol. Replacement values are copied into the result without further interpretation. Raises SubstitutionSyntaxError if there are malformed constructs in s.


Returns True if s is a valid name for a substitution text, otherwise returns False.


>>> from ZConfig.substitution import substitute
>>> d = {'name': 'value',
...      'top': '$middle',
...      'middle' : 'bottom'}
>>> substitute('$name', d)
>>> substitute('$top', d)