Strings

Question 1

What is: - String Concatenation?
- String Multiplication
- String length

Answer 1

Processing strings

• Joins strings i.e “Hello” + “ “ + ”World”
• Multiplies a string i.e “Hello”*3 = HelloHelloHello
• Finds the length of a string I.e len(“ciao) = 4

Question 2

Indexing Strings
- Where does it start?
- What does it do?
- How to do it?

Answer 2

• Starts at 0 not 1
• Returns the single character
• “string”[i]
• i.e “Hello World”[6] = W

Question 3

What does:
- Ord(“a”) do?
- Chr(97) do?
- Int(“1234”)
- Str(1234)

Answer 3

• Returns the Unicode number for 1-character string a
• Returns 1-character string with Unicode symbol 97
• returns integer value 1234
• Returns the string value 1234

Question 4

Slicing
What is the syntax?
Where does the backward indexing start?
How to slice from back to front?
Are the parameters optional?
What is essential?

Answer 4

• Syntax: Variable[Start:Stop:Step]
• Starts at -1
• If Step is negative
• Start is optional, assumed as 0 if no step. -1 if step is negative
  Stop is optimal, assumed to be Len, -Len-1 if step is negative
  Step is optional, assumed as 1
• At least one colon must be included - even if all parameters are left out

Question 5

String Functions
- Syntax
- How to look for the integer number?
- How to teeny position of first string y in x?
- How to return lower case?
- How to return upper case?
- How to return a version of string_x with every occurrence of string y replaced with new?

Answer 5

Syntax - string_x.function(string_y)
- Count — string_x.count(string_y)
- Find — string_x.find(string_y)
- Lower — Bro.lower()
- Upper — Bro.upper()
- Replace — String_x.replace(string_y, new)

Question 6

Format
I.e - “{0:<20}”.format(“one”)
- “{0:>20}”.format(“one”)
- “{0:^20}”.format(“one”)
- “{0:5.3f}”.format(1.23456789)

Answer 6

• Left- aligned in fixed width
  “One “
• Right-aligned in fixe width
  “ One”
• Centered in fixed width
  “ One “
• Floating point number rounding
  “1.235”

Question 7

Examples. What do these produce?
a = “Jabberwocky”

— b = a[::2]
— c = a[::-2]
— d = a[0:5:2]
— e = a[5:0:-2]
— f = a[:5:1]
— g = a[:5:-1]
— h = a[5::1]
— i = a[5::-1]
— j = a[5:0:-1]

Answer 7

• “Jbewcy”
• “ycwebJ”
• “Jbe”
• “rba”
• “Jabbe”
• “ykcow”
• “rwocky”
• “rebbaJ”
• “rebba”