Graphical User Interfaces
For the majority of computer users, as compared to developers or data scientists, a
graphical user interface (GUI) is what they are used to. Such a GUI does not only bring
along visual appeal and simplicity; it also allows us to guide and control user interaction
much better than alternative approaches like interactive scripting, or use of a command
line interface or shell. In what follows, we build on the examples of the previous section
and build simple GUIs for our short rate and cash flow series classes.
To build the GUIs we use the traits library, documentation of which you can find at
for rapid GUI building on top of existing classes and only seldom for more complex
applications. In what follows, we will reimplement the two example classes from before,
taking into account that we want to use a GUI for interacting with instances of the
respective classes.
Short Rate Class with GUI
To start, we need to import the traits.api sublibrary:
In [ 72 ]: import numpy as np
import traits.api as trapi
For the definition of our new short_rate class, we use the HasTraits class to inherit
from. Also note in the following class definition that traits has its own data types, which
are generally closely intertwined with visual elements of a GUI — to put it differently,
traits knows which graphical elements (e.g., for a text field) to use to build a GUI
(semi)automatically:
In [ 73 ]: class short_rate(trapi.HasTraits):
name = trapi.Str
rate = trapi.Float
time_list = trapi.Array(dtype=np.float, shape=( 5 ,))
def get_discount_factors(self):
return np.exp(-self.rate * self.time_list)
Instantiation of such a traits-based class is done as usual:
In [ 74 ]: sr = short_rate()
However, via a call of the method configure_traits (inherited from HasTraits) a GUI is
automatically generated, and we can use this GUI to input values for the attributes of the
new object sr:
In [ 75 ]: sr.configure_traits()
Figure 13-4 shows such a simple GUI, which in this case is still empty (i.e., no input
values have been put in the different fields). Note that the lower five fields all belong to
“Time list” — this layout is generated by default.
Figure 13-5 shows the same simple GUI, this time however with values in every single
field. Pushing the OK button assigns the values from the input fields to the respective
attributes of the object.
