After a block-opening statement, the next line is indented by 4 spaces (in thePython Shell window by one tab). After certain keywords (break, return etc.)the next line is dedented. In leading indentation, Backspace deletes upto 4 spaces if they are there. Tab inserts spaces (in the PythonShell window one tab), number depends on Indent width. Currently, tabsare restricted to four spaces due to Tcl/Tk limitations.