Regex

Question 1

Regular expressions

Answer 1

A language independent approach to expressing patterns

Question 2

Hierarchy of languages

Answer 2

Type 0: unrestricted grammars
Type 1: context-sensitive grammars
Type 2: context-free grammars
Type 3: regular grammars

Type 2 used in parsers
Type 3 used in regular expressions and lexical analyzers

Question 3

Grep

Answer 3

Global regular expression print

• arg 1: a regex
• arg 2: a set of files where grep will try to find strings matching regex

Answer 4

Start with

Question 5

[^]

Answer 5

Not in set

Question 6

.

Answer 6

Any char

Question 7

-w

Answer 7

Contains that specific word

Question 8

-i

Answer 8

Case insensitive

Question 9

$

Answer 9

Ends with

Question 10

a*

Answer 10

Zero or more reps of ‘a’

Question 11

a+

Answer 11

one or more reps of ‘a’

Question 12

a?

Answer 12

Zero or one rep of ‘a’

Question 13

a{5}

Answer 13

Exactly 5 reps of ‘a’

Question 14

a{3,7}

Answer 14

3 to 7 reps of ‘a’

Question 15

[abc]

Answer 15

Any one char in the set

Question 16

a|b

Answer 16

Match ‘a’ or ‘b’

Question 17

()

Answer 17

Group a component of symbols in the regex

Question 18

\

Answer 18

Escape any meta symbol

Question 19

\d

Answer 19

Any decimal digit

Question 20

\w

Answer 20

Any alphanumeric char

Question 21

\s

Answer 21

Any white space char

Question 22

\b

Answer 22

Empty string at a word boundary

Question 23

\D

Answer 23

Match any non-digit char

Question 24

\W

Answer 24

Match any non-alphanumeric char

Question 25

\S

Answer 25

Match any non-white spice char

Question 26

\B

Answer 26

Empty string not at a word boundary

Question 27

\number

Answer 27

Matches text of group number

Question 28

re.match()

Answer 28

(string, pattern) | Return address

Question 29

re.compile()

Answer 29

Can use to reuse patterns | Helps to gain speed

Question 30

Word boundary

Answer 30

The first letter that starts a given word

Question 31

re.search()

Answer 31

Provides us with index (gives first index of first match - returns none if not found - but r in front to look at the raw text