1. CSE 231 Lab 3

2. Topics to cover Strings Basics String Slicing String Comparison
String Methods
Patterns to Build Strings
String Formatting

3. Strings basics review H e l o W r d 1 2 3 4 5 6 7 8 9 10
>> input_str = ‘Hello World’ H e l o W r d 1 2 3 4 5 6 7 8 9 10
>> print(input_str)?
>> print(type(input_string))?
>> print(len(input_str))?
>> print(input_str[1])?
Hello World
<class 'str'> 11 e

4. Strings basics review H e l o W r d 1 2 3 4 5 6 7 8 9 10 -11 -10 -9 -8
>> input_str = ‘Hello World’ H e l o W r d 1 2 3 4 5 6 7 8 9 10
-11
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1
>> print(input_str[-1])? d
>> print(input_str[-5])? W
>> print(input_str[-10])? e

5. Slicing
Start
end
input_str[ : ]
Does not include
Includes

6. >> input_str = ‘Hello World’1 2 3 4 5 6 7 8 9 10
-11
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1
>> print(input_str[6:10])?
Worl
>> print(input_str[6:11])?
World
>> print(input_str[6:])?
World
Hello
>> print(input_str[:5])?
Hello
>> print(input_str[0:5])?
>> print(input_str[3:-2])?
lo Wor

7. Extended Slicing H e l o W r d 1 2 3 4 5 6 7 8 9 10 -11 -10 -9 -8 -7
>> input_str = ‘Hello World’ H e l o W r d 1 2 3 4 5 6 7 8 9 10
-11
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1
>> print(input_str[::2])?
HloWrd
>> print(input_str[::-2])?
drWolH
>> print(input_str[1::2])?
el ol

8. String comparison
‘a’ < ‘b’
‘hi’ > ‘hello’
ASCII table

9. String Methods
Methods are like functions but specific to certain classes
.isupper() #checks if entire string is upper case
.isdigit() #checks if entire string is a digit (number)
.isalpha() #checks if entire string is all letters(word)
.lower() #converts string to all lower case
.find(ch) #returns the first index where ch is found, -1 if not
.rfind(ch) #returns the last index where ch is found, or -1 if not
.replace(old, new) #returns a new string where all occurrences of old substring is replaced with new substring.

10. Patterns to build string
Ints:
x = 0 # initialize at zero
x += 1 # increment the counter
Strings:
s = ‘’ # initialize with empty string
s += ch # concatenate characters

11. String Formatting price = 2000 str1= ‘Price’
print('{ } is ${ }'.format(str1, price))
Price is $2000
#What gets printed?

12. String Formatting {:[align] [minimum_width] [.precision] [descriptor]}
>> price = 2000
>> print('{ }'.format(price))
{:[align] [minimum_width] [.precision] [descriptor]}
>> print('{:>10,d}'.format(price))
2,000
|__________|
10 spaces
#What gets printed?

13. String Formatting

14. Enumerate: Alphabet = ‘michigan’ for c, value in enumerate(Alphabet):
print(c, value)
2 m
3 i
4 c
5 h
6 i
7 g
8 a
9 n
Alphabet = ‘michigan’
for c, value in enumerate(Alphabet, 2):
print(c, value)

15. String Formatting s : string d : decimal integer
f : floating point decimal
Demo: lab03.pre-lab.part_D.py