AOIT Introduction to Programming Unit 3, Lesson 10 Advanced Sequence Manipulation Copyright © 2009–2012 National Academy Foundation. All rights reserved.

Methods and functions make sequences more powerful Examples: String methods can test strings: "abCde".isalpha() returns True String methods can change strings: "abCde".lower() returns "abcde" List and tuple functions can return information: Given mytuple = ("horse","cow","sheep") len(mytuple) returns 3 If you applied the len() function to the suit_string tuple in the Shuffle Cards program, what would you get?

String-testing methods test to see whether a string has a certain form Prior Program: New Password New Program: Hangman Key Characteristics: Returns True or False Examples: string.isalnum() string.isalpha() string.isnumeric() # string contains only letters or numbers # string contains only letters # string contains only numbers What do you suppose string.islower() does?

Case-changing methods change the case of a string Prior Programs: Menu and Vacation New Program: Hangman Key Characteristics: Operates on (makes a change in) a string Examples: string.capitalize() string.lower() string.upper() # capitalize the first character # convert to lowercase # convert to uppercase What do you suppose string.swapcase() does?

String-formatting methods format string (text) output Prior Program: Menu New Program: Hangman Key Characteristics: Formats printed output Examples: string.center(width) string.ljust(width) You will use these methods in the text art for Hangman. # center string within a given width # left-justify string What is the method to right-justify? What does right-justify mean?

Escape sequences are useful in formatting text Note: sequence here means “a string of characters” Backslashes (\) are used in Python programs to insert special characters into strings. An example you have seen before (in the Menu and Vacation programs) is \t, which moves the cursor forward one tab stop. Another example is \", which prints a double quote. You might find escape sequences useful in the text art for Hangman. What is the escape sequence to print a single quote?

find() is the most useful string-searching method The find() method finds the first occurrence of a substring in a string. find() returns the lowest index where the substring is found, and it returns -1 if it is not found. The format is string.find(substring). An example is "abcd".find("a"), which returns 0. What do you think "abcd".find("c") returns? What do you think "abcd".find("e") returns?

The string-stripping and string-replacement methods change strings Prior Program: Vacation New Program: Hangman Key Characteristics: Makes changes to strings Examples: "cat".replace("t","b") returns 'cab' " 12A B ".strip() returns '12A B' String-stripping is used in Hangman. What do you think "Happy Birthday! ".strip() returns?

Hangman uses several list and tuple methods and functions Prior Program: Shuffle Cards New Program: Hangman Names: append(), pop(), join(), and len() Examples (from Shuffle Cards): cards.append(card_string) return deck.pop(0) How would you return the last card in the deck? # append each card string in turn # to the end of the list of cards # return the first card in the deck # to the calling function # and remove it from the list

Hangman uses several list and tuple methods and functions (continued) Examples (from Hangman): print(''.join(guesses)) word_len = len(theword) If the word is antelope, what value is assigned to word_len? # print the letters correctly guessed # if the word is hyena and the player has guessed a # then join() returns '_ _ _ _a' (four underscores and an a) # assign the length of the word # to the variable word_len

Methods and functions are used extensively with sequences You have used many methods and functions in prior programs. You will be using a number of methods and functions in the Hangman minor project and in your culminating project. It is helpful to categorize methods and functions based on what they do and on what kind of sequences they work with. For more information about methods and functions, see the course’s QuickStart Guide.