Python String Manipulation and Graphs

Question 1

What is a raw string?

Answer 1

Suppresses blackslashes in string.
Make one by putting r before first quote e.g. r”some text”
It’s type is str just like regular strings

Question 2

What is __doc__?

Answer 2

-If the first thing in a function or class body is a string literal,
it is stored in the \_\_doc\_\_ attribute of the function/class
-Can also be unicode strings

Question 3

What data type does python not have?

Answer 3

character

Question 4

Get the length of a string

Answer 4

– len(string)

Question 5

Access a character in the string with subscript notation

Answer 5

– c = string[1]

Question 6

● Access a substring of a string with slice notation

Answer 6

– sub = string[1:5]

Question 7

● Reverse a string by using slice notation with a negative step

Answer 7

– rev = string[::-1]

Question 8

● Iterate over the characters of a string

Answer 8

– for c in string:

Question 9

Convert a string to an array of strings split on a given

separator

Answer 9

– arr = string.split(separator)

Question 10

Concatenate an array of strings into a single string, inserting a separator between each

Answer 10

– s = separator.join(Iterable)

Question 11

Standard approach to build a String Character-by-Character

Answer 11

The standard approach is to build an array of singlecharacter strings, then use join()

Question 12

What are the string predicates?

Answer 12

Test type of characters in string; return true if nonempty and all characters are of the specified type

Question 13

How do you capitalize the first character in a string?

Answer 13

cap = string.capitalize() first char uppercased, rest lowercased

Question 14

How do you uppercase->lowercase and vice versa?

Answer 14

– swp = string.swapcase()

Question 15

How do you capitalize the first character in every word?

Answer 15

– tc = string.title()

Question 16

How to check if a substring is a prefix

Answer 16

b = string.startswith(sub)

Question 17

How to check if a substring is a suffix

Answer 17

b = string.endswith(sub)

Question 18

How to get the index of a substring (2)

Answer 18

– idx = string.find(sub) index of first occurrence of sub or -1
– idx = string.rfind(sub) index of last occurrence of sub or -1

Question 19

How to count number of occurences of substring in a string

Answer 19

string.count(sub) (can’t be overlapping)

Question 20

Replace occurrences of a substring with a new string with and without a limit number (2)

Answer 20

– rep = string.replace(old,new) all occurrences

– rep = string.replace(old,new,count) at most count occur

Question 21

Partition string around a separator (2)

Answer 21

– (before, sep, after) = string.partition(sep) use first occur of sep
– (before, sep, after) = string.rpartition(sep) use last occur of sep
The separator can be a regex!

Question 22

add spaces to center string in width

Answer 22

– j = string.center(width)

Question 23

add spaces to start/end as needed

Answer 23

– j = string.[lr]just(width)

Question 24

add leading zeros to number as needed

Answer 24

– n = string.zfill(width)

Question 25

Remove leading and trailing spaces from string (3)

Answer 25

– s = string.strip() remove leading and trailing whitespace
– s = string.lstrip() remove leading whitespace
– s = string.rstrip() remove trailing whitespace

Question 26

use conversion specifier with format function

Answer 26

“Hello, {conversion_specifier}”.format(some_number)

Question 27

Conversion specifier for 3 digit zero padded decimal

Answer 27

%03d

Question 28

For f string, when is value evaluated?

Answer 28

value is evaluated at run-time

Question 29

What are the magic functions for string formatting? (3)

Answer 29

-__str__ is called by print() to convert an object to a readable string
– __repr__ converts an object into an unambiguous string representation; it is called by the default __str__() for containers, by print() if __str__ is not defined, and by str.format() and f-strings if the !r conversion specifier is given
– __format__ is called by str.format() and f-strings if formatting options are present

Question 30

Check if string contains only letters or digits

Answer 30

– b = string.isalnum()

Question 31

Check if string contains only characters valid for forming a number

Answer 31

– b = string.isnumeric()

Question 32

Check if string contains only characters valid for a radix-10 number

Answer 32

– b = string.isdecimal()

Question 33

Check if string contains only letter (uppercase or lowercase)

Answer 33

– b = string.isalpha()

Question 34

Check if string contains only lowercase letter

Answer 34

– b = string.islower()

Question 35

Check if string contains only uppercase letter

Answer 35

– b = string.isupper()

Question 36

Check if string contains only digits

Answer 36

– b = string.isdigit()

Question 37

Check if string contains only whitespace

Answer 37

– b = string.isspace()

Question 38

What type do you use for regex in python?

Answer 38

raw strings