Input and Output with Data Entry Fields

Three types of data entry fields appear in breezypythongui: IntegerField, and FloatField, and TextField.  As the names imply, each type of field is suited for the input and output of a specific type of data.  In the case of the numeric fields, conversion between numbers and text is handled internally within the field object.  Thus, the input method getNumber returns a number, whereas the output method setNumber expects a numeric argument, when used with the numeric fields.  The FloatField method setPrecision is available to modify the precision used to display numbers.  The methods getText and setText are used to read and write strings with text fields.  The data entry field methods are summarized in the next table:

Field Type	Method	What it does
IntegerField, FloatField	getNumber()	Returns (as input) the number contained in the field.
	setNumber(number)	Outputs the number to the field.
FloatField	setPrecision(width)	Sets the number of digits to display to right of the decimal point.
TextField	getText()	Returns (as input) the string contained in the field.
	setText(text)	Outputs the string to the field.

To make a data field output only, to prevent the user from editing its contents, the programmer can set its state attribute to the tkinter constant "readonly".

Note that the input method getNumber raises an exception if the user has entered a number with an invalid format (such as bad digits).  This type of error can be trapped under program control with a try-except statement (see Message Boxes).