##
2.7.1 ProgressBar Objects

`ProgressBar` objects provide support for modeless progress-bar dialogs. Both determinate (thermometer style) and indeterminate (barber-pole style) progress bars are supported. The bar will be determinate if its maximum value is greater than zero; otherwise it will be indeterminate. Changed in version 2.2: Support for indeterminate-style progress bars was added.

The dialog is displayed immediately after creation. If the dialog's ``Cancel'' button is pressed, or if `Cmd-.` or `ESC` is typed, the dialog window is hidden and `KeyboardInterrupt` is raised (but note that this response does not occur until the progress bar is next updated, typically via a call to `inc()` or `set()`). Otherwise, the bar remains visible until the `ProgressBar` object is discarded.

`ProgressBar` objects possess the following attributes and methods:

`curval`
  The current value (of type integer or long integer) of the progress bar. The normal access methods coerce `curval` between `0` and `maxval`. This attribute should not be altered directly.

`maxval`
  The maximum value (of type integer or long integer) of the progress bar; the progress bar (thermometer style) is full when `curval` equals `maxval`. If `maxval` is `0`, the bar will be indeterminate (barber-pole). This attribute should not be altered directly.

`title`( | [newstr])

  Sets the text in the title bar of the progress dialog to newstr.

`label`( | [newstr])

  Sets the text in the progress box of the progress dialog to newstr.

`set`( | value[, max])

  Sets the progress bar's `curval` to value, and also `maxval` to max if the latter is provided. value is first coerced between 0 and `maxval`. The thermometer bar is updated to reflect the changes, including a change from indeterminate to determinate or vice versa.

`inc`( | [n])

  Increments the progress bar's `curval` by n, or by `1` if n is not provided. (Note that n may be negative, in which case the effect is a decrement.) The progress bar is updated to reflect the change. If the bar is indeterminate, this causes one ``spin'' of the barber pole. The resulting `curval` is coerced between 0 and `maxval` if incrementing causes it to fall outside this range.