PiZero W connected to two peripherals (GPIO and USB): how to continuously read from both at same time?

I have a raspberry pizero W that is connected via GPIO pins to a flowmeter and USB to a barcode scanner. I have python script that uses a callback function to be alerted when the GPIO input is sensed. This python script needs to be continuously running on the pizero in order to recognize when the flowmeter is activated and process the input.

Changing position of vertical (z) axis of 3D plot (Matplotlib)?

I’m doing some 3D surface plots using Matplotlib in Python and have noticed an annoying phenomenon. Depending on how I set the viewpoint (camera location), the vertical (z) axis moves between the left and right side. Here are two examples: Example 1, Axis left, Example 2, Axis right. The first example has ax.view_init(25,-135) while the second has ax.view_init(25,-45).