Effective Strategies for Solving Programming Problems

CSE 231 LAB 3

TOPICS TO COVER How to solve a problem Strings Basics String Slicing String Comparison String Methods Patterns to Build Strings String Formatting

HOW TO SOLVE A PROBLEM Do not do everything at once! Solve the problem in your own words and write it down (written steps, flowcharts, or maybe pseudo code) Once you have a solution, translate it to Python and adjust as needed This significantly reduces the complexity of getting a solution.

HOW TO SOLVE A PROBLEM Break it down. Any problem is the sum of many smaller and more manageable pieces. When reading the PDF/ directions, identify key words and phrases (I.E. What happens, what it happens to, what the result is, and how it happens). Ex. Create a program that, given 2 integers [Start with this], returns [indicates the result is next] the greatest common divisor[result] without using math module [restriction] Check the FAQ for the projects on Piazza.

STRINGS

STRINGS BASICS REVIEW >> input_str = Hello World H e l 0 1 l 3 o 4 W o r 6 7 l d 9 10 2 5 8 >> print(input_str)? Hello World <class 'str'> >> print(type(input_string))? >> print(len(input_str))? 11 >> print(input_str[1])? e

STRINGS BASICS REVIEW >> input_str = Hello World H 0 e 1 l l o W o r l d 2 3 4 5 6 7 8 9 10 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 >> print(input_str[-1])? d >> print(input_str[-5])? W >> print(input_str[-10])? e

SLICING Start end input_str[ : ] Does not include Includes

>> input_str = Hello World H 0 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 e 1 l l o 3 W o 6 r 8 l d 2 4 5 7 9 10 Worl World >> print(input_str[6:10])? >> print(input_str[6:11])? World Hello >> print(input_str[6:])? >> print(input_str[:5])? Hello >> print(input_str[0:5])? lo Wor >> print(input_str[3:-2])?

EXTENDED SLICING >> input_str = Hello World H 0 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 e 1 l l o 3 W o 6 r 8 l d 2 4 5 7 9 10 >> print(input_str[::2])? HloWrd >> print(input_str[::-2])? drWolH >> print(input_str[1::2])? el ol

STRING COMPARISON a < b hi > hello ASCII table

STRING METHODS Methods are like functions but specific to certain classes .isupper() #checks if entire string is upper case .isdigit() #checks if entire string is a digit (number) .isalpha() #checks if entire string is all letters(word) .lower() #converts string to all lower case .find(ch) #returns the first index where ch is found, -1 if not .rfind(ch) #returns the last index where ch is found, or -1 if not .replace(old, new) #returns a new string where all occurrences of old substring is replaced with new substring.

PATTERNS TO BUILD STRING Ints: x = 0 x += 1 Strings: s = s += ch # initialize at zero # increment the counter # initialize with empty string # concatenate characters

ENUMERATE: 0 m 1 i 2 c 3 h 4 i 5 g 6 a 7 n Alphabet = michigan for c, value in enumerate(Alphabet): print(c, value) 2 m 3 i 4 c 5 h 6 i 7 g 8 a 9 n Alphabet = michigan for c, value in enumerate(Alphabet, 2): print(c, value)

STRING FORMATTING: 1- Using .format() method: price = 2000 str1= Price print('{ } is ${ }'.format(str1, price)) Price is $2000 #What gets printed? 2- Using fstrings method: print(f'{str1} is ${price }') Price is $2000 #What gets printed?

STRING FORMATTING 1- Using .format() method: { {:[align] [minimum_width] [.precision] [descriptor]} } >> price = 2000 >> print('{:>10,d}'.format(price) 2,000 |__________| 10 spaces #What gets printed? 2- Using fstrings method: { {variable:[align] [minimum_width] [.precision] [descriptor]} } >> print(f' {price:>10,d}') #What gets printed?

STRING FORMATTING s : string d : decimal integer f : floating point decimal Demo: Demo_Lab03.py LAB03 Part A Debugging: debug3.py