11.1.4. Specifying field values and identifiers

Fields for entering text (e.g. names, source code) are tajken literary. Fields for entering variables, parameters, options, and settings accept several data types

  • integer and real numbers are treated as Python scalars of type int and float

  • strings True and False are treated as scalar boolean values

  • all other strings not containing whitespace are treated as strings

  • space separated values are treated as lists

This has several limitations. For instance, you cannot specify a string containing whitespace. You also cannot specify an empty list or a list with no members. For such cases you can use the hash notation

#<Pythonic expression>

One would specify an empty list and a list with one element as


The expression will be evaluated when the data in the GUI are dumped to a file, unless otherwise noted. The variables which were defined in the project are available in the evaluation environment.

The following hashed entries in the GUI result in identical dumped values



hello 3 4 5
#['hello', 3, 4, 5]

Identifiers are strings conforming to some simple rules.

  • An identifier comprises only numbers, English letters, and underscores.

  • It never starts with a number.

They are used for naming things in PyOPUS and the GUI.