Q.Write a program to count the number of times a character appears in a given string.

A teacher marking attendance does not glance at the room and guess — she goes down the register one name at a time, keeping a running tally. Character counting in a program works the same way: a string is a sequence of characters, and to count something inside it you visit each character in turn and keep a tally of the ones that qualify. The skill being taught is not really "counting"; it is controlled traversal with a running total, one of the most reusable patterns in all of programming.

Python gives three levels of tool, and choosing the right one is part of the concept: …