Question

8.17 python

a.) Write a regular expression pattern to match all words ending in s.

b.) Write a regular expression pattern to match all words ending in ing.

c.) Write a regular expression pattern to match all words with ss anywhere in the string.

d.) Write a regular expression pattern to match all words beginning and ending with the letter a.

e.) Write a regular expression pattern to match all the words that start with st.

f.) Write a regular expression to match all the four-letter words where the middle two letters are vowels.

Answer 1

a) "[a-zA-Z]+s\b" - [a-zA-Z] denotes any alphabetic character, + indicates one to many of those preceding types which in this case is alphabets, s\b indicates that the word ends with s

b) "[a-zA-Z]+ing\b" - [a-zA-Z] denotes any alphabetic character, + indicates one to many of those alphabets, ing\b indicates that the word ends with ing

c) "[a-zA-Z]*ss[a-zA-Z]*" - [a-zA-Z] denotes any alphabetic character, * indicates zero or more of those preceding types which in this case is alphabets, followed by ss followed by zero or more alphabets again

d) "\ba[a-zA-Z]*a\b" - \ba denotes a word starting with a, then zero or more alphabets and then a\b denotes a word ending with a

e) "\bst[a-zA-Z]*" - \bst denotes a word starting with st, then zero or more alphabets

f) "\b[a-zA-Z][aeiou][aeiou][a-zA-Z]\b" - first \b denotes a word starting boundary following by a character of alphabet in the range a-z or A-Z . This is following by two characters that are vowels denoted by[aeiou] which means any of these. and finally again a normal alphabet following by \b which denotes a word boundary in this case the word end. you can also use[aeiouAEIOU] for case insensitive vowels in the middle.