Advanced Strings

Strings -- List of Characters

Characters can be:

• Letters [A-Za-z]
• Numbers [0-9]
• Symbols [@ $ # ~ ]
• Unicode Characters Site
• Spaces [' ']
• Escape Character [\n \r \t \' \\ \b \f \ooo \xhh]

String Indexing

• Each character has an index

Char#	1	2	3	4	5	6	7	8	9	10	11
Char	W	E	B	E	R		S	T	A	T	E
+ Index	0	1	2	3	4	5	6	7	8	9	10
- Index	-11	-10	-9	-8	-7	-6	-5	-4	-3	-2	-1

# Select characters out of a string
school = 'WEBER STATE'
print ('character 1 :' + school[0])        -->
print ('character 4 :' + school[3])        -->
print ('character 7 :' + school[-4])       -->

Slicing Strings

• SYNTAX -- string [start : end]

  • begin at start and extending up to but not including end
  • school[0:3] --> WEB
  • start blank
    • start at index 0
    • school[:3] r--> WEB
  • end blank
    • go until the end of the string
    • school[8:] --> ATE

# Select a substring
print ('start = 0 end = 4: ' + school[0:4])    --> 
print ('start = 0 end = 5: ' + school[0:5])    -->

print ('start = 2 end = 5: ' + school[2:5])    -->
print ('start = -5 end = : ' + school[-5:-1])  -->

print ('start = -5 end = : ' + school[-5:])    -->
print ('start =  end = : ' + school[:])        -->

• String have a length property

Combining Strings

• String Operators

• + concatenate (combine strings)
• * create multiple copies of the string

# combine string
a = 'apple'
b = 'sauce'

print (a + b)       -->
print (a + b + a)   -->


print (a * 3)       -->
print (3 * a)       -->

Formating Strings

• Can't combine strings and numbers unless you use format

# This will produce a TypeError
age = 75
person = 'Scott is ' + age
print (person)
  
#Using the format string method
age = 75
person = 'Scott is {}'
print (person.format(age))

#Using the format string method for multiple items
age = 75
hours = 10
person = 'Scott is {} he sleeps {} hours a day'
print (person.format(age, hours))

#Using the format string method for multiple items with index
age = 75
hours = 10
dogs = 5
person = 'Scott sleeps {1} hours a day. He is {0} years old. He has {2} dogs'
print (person.format(age, hours, dogs))

Escape characters and strings

• illegal characters in a string require an escape character
• Use \ followed by the character
• Escape Character [\n \r \t \' \\ \b \f \ooo \xhh]

# use of single quote in string
txt = "Scott's Dog"
# or
txt = 'Scott\s Dog'
  
#Using the format string method
age = 75
person = 'Scott is {}'
print (person.format(age))

#Using the format string method for multiple items
age = 75
hours = 10
person = 'Scott is {} he sleeps {} hours a day'
print (person.format(age, hours))

#Using the format string method for multiple items with index
age = 75
hours = 10
dogs = 5
person = 'Scott sleeps {1} hours a day. He is {0} years old. He has {2} dogs'
print (person.format(age, hours, dogs))

Common string methods

• capitalize() first character to uppercase
• title() first character of each word to uppercase
• casefold() lowercase
• len() return the length of the string
• count() number of times a value occurs in a string
• additional string methods

# capitilize the first letter
name = 'scott'
print (name.capitalize())

name = 'sCoTt'
print (name.capitalize())

More info on Strings

• realpython.org -> Strings
• w3schools.org -> Strings
• python.org -> Strings