How to add space between two widgets placed in grid in tkinter ~ python?

When you pack the widget you can use

self.a_button = Button(root, text="A Button") 
self.a_button.grid(row=0, column=1, padx=10, pady=10)

Using padx and pady you can add padding to the outer side of the button and alternatively if you want to increase the size of the button you can add inner padding using ipadx and ipady.

If you want more on the Grid function you can view all the options and uses here.