# 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

#[]
#['element']


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

100
#100
#50+50

True
#True
#1==1

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.