Based on the setting of first day of the week, the calendar first weekday can be set. Week day number starts from 0 as Monday , 1 as Tuesday and ends at 6 as Sunday.
import calendar
x=calendar.TextCalendar()
x.setfirstweekday(4) # first week day is Friday
x.prmonth(theyear=2020,themonth=7,w=3,l=0)