Strings

Question 1

Ways to indicate a string.

Answer 1

’ ‘

” “

””” “””

Question 2

Len(str) function

Answer 2

Determines the number of characters in a string.

> > > Len(‘pear’)
4

Empty string = ‘ ‘, “ “

Question 3

String concatenation

Answer 3

’+’ = adds together strings

‘*’ = multiples the strings, ie concatenates many times

Question 4

String definition

Answer 4

A sequence of one or more characters. Includes letters, numbers, punctuation, symbols, etc.

Question 5

String indexing is used for what?

Answer 5

To access the individual characters of a string.

S= ‘apple’

S[0] = ‘a’

Square brackets are used to index strings.

Starts at “0”, 1, …

-1 is last character in negative indexing

Question 6

What is the character encoding scheme used now?

Answer 6

Unicode

Replaced ASCII

Question 7

ord(‘a’) = ?

Answer 7

Returns the character code for that character.

ord function

> > > ord(‘a’)
97

Question 8

chr(97) = ?

Answer 8

Finds the character, given the character code

chr function

> > > chr(97)
‘a’

Question 9

What are ‘whitespace characters ‘?

Answer 9

Characters that appear as blanks on the printed page.

\\ = \
\' = '
\" = "
\n = new lone
\r = return (carriage return)
\t = tab

Question 10

Slicing strings

Answer 10

How python lets you extract a substring from a string.

s[begin:end]

Starts at ‘begin ‘ and ends at (end - 1)

s[ :5] = from beginning to 4

s[5: ] = from 5 to end

Question 11

String-testing functions

Answer 11

Test if a string has a certain form.
Returns a True or False
Also called Boolean functions or predicates

Question 12

s.endswith(t)

Answer 12

String-testing functions, returns True when

s ends with string t

Question 13

s.startswith(t)

Answer 13

String-testing functions, returns True when

s starts with string t

Question 14

s.isalnum()

Answer 14

String-testing functions, returns True when

s contains only letters or numbers

Question 15

s.isalpha()

Answer 15

String-testing functions, returns True when

s contains only letters

Question 16

s.isdecimal()

Answer 16

String-testing functions, returns True when

s contains only decimal characters

Question 17

s.isdigit()

Answer 17

String-testing functions, returns True when

s contains only digits

Question 18

s.isidentifier()

Answer 18

String-testing functions, returns True when

s is a valid Python identifier (that is, name)

Question 19

s.islower()

Answer 19

String-testing functions, returns True when

s contains only lowercase letters

Question 20

s.isnumeric()

Answer 20

String-testing functions, returns True when

s contains only numeric characters

Question 21

s.isprintable()

Answer 21

String-testing functions, returns True when

s contains only printable characters

Question 22

s.isspace((

Answer 22

String-testing functions, returns True when

s contains only whitespace characters

Question 23

s.istitle()

Answer 23

String-testing functions, returns True when

s is a title-case string

Question 24

s.isupper()

Answer 24

String-testing functions, returns True when

s contains only uppercase letters

Question 25

t in s

Answer 25

String-testing functions, returns True when

s contains t as a substring

Question 26

String-searching functions

Answer 26

Way to find substrings within a string

Find - if not in string, returns a ‘ValueError’

Index - if not in string, returns a ‘-1’

Question 27

s.find(t)

Answer 27

Returns-1, or index where t starts in s

rfind(t) - searches right to left

Question 28

s.index(t)

Answer 28

Returns ValueError, or index where t starts in s

rindex(t) - searches right to left

Question 29

s.capitalize()

Answer 29

s[ ] is made uppercase

Question 30

s.lower()

Answer 30

All letters of s are made lowercase

Question 31

s.upper()

Answer 31

All letters of s are made uppercase

Question 32

s.swapcase()

Answer 32

Lowercase are made upper, and vice versa

Question 33

s.title()

Answer 33

Title-case version of s

Question 34

s.strip(ch)

Answer 34

Removes all ch characters in t occurring at the beginning or end of s

Question 35

s.replace(old, new)

Answer 35

Replaces every occurrence of old within s with new

Question 36

s.expandtabs(n)

Answer 36

Replaces each tab character in s with n spaces

Question 37

s.count(t)

Answer 37

Number of times t occurs within s

Question 38

s.encode()

Answer 38

Sets the encoding of s

Question 39

s.join(seq)

Answer 39

Concatenates the strings in seq, using s as a separator

Question 40

s.maketrans(old, new)

Answer 40

Creates a translation table used to change the characters in old with the corresponding characters in new

Question 41

s.translate(table)

Answer 41

Makes the replacementsin s using the given translation table created with maketrans

Question 42

s.zfill(width)

Answer 42

Adds enough ‘0’s’ to the left of s to make a string of length ‘width ‘

Question 43

Regular expressions

Answer 43

Is a way to compactly describe a set of strings.

Question 44

What set of strings does xy? describe?

Answer 44

x, xy

? = character to the left of this is optional.

‘Cats?’ = cat, cats

Question 45

What set of strings does ‘x|y’ describe?

Answer 45

x|y = x, y

’|’ = or

Question 46

What set of strings does ‘x*’ describe?

Answer 46

x* = ‘ ‘, x, xx, xxx, xxxx, …

Question 47

What set of strings does ‘x+’ describe?

Answer 47

x+ = x,xx,xxx,xxxx, ….

Question 48

What set of strings does ‘(ha)+!’ Describe?

Answer 48

= ha!, haha!, hahaha! …

Question 49

What set of strings does ‘ha+!’ Describe?

Answer 49

= ha!, haa!, haaa!, ….