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

Strings in Python are sequences of characters, where each character has an index (positive or negative).

Positive indexing starts at 0 and goes from left to right. Negative indexing starts at -1 and goes from right to left.

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 .format()
age = 25
name = "Alice"
print("{} is {} years old.".format(name, age))
# Output: Alice is 25 years old.

Using f-strings (Python 3.6+)

print(f"{name} is {age} years old.")

Output: Alice is 25 years old.

#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))

hours = 8 dogs = 2 print("{0} sleeps {1} hours and owns {2} dogs.".format(name, hours, dogs))

Output: Alice sleeps 8 hours and owns 2 dogs.

Escape Characters in Strings

Escape characters allow you to include special characters in strings:

• \': Single quote
• \\: Backslash
• \n: Newline
• \t: Tab

Code Example:

# Using escape characters
quote = 'It\'s a beautiful day!'
path = "C:\\Users\\Alice\\Documents"
print(quote)  # Output: It's a beautiful day!
print(path)   # Output: C:\Users\Alice\Documents



## 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](https://realpython.com/python-strings/#built-in-string-methods)

>```python
># capitilize the first letter
> name = 'scott'
> print (name.capitalize())
> 
> name = 'sCoTt'
> print (name.capitalize())




## More info on Strings
- [realpython.org -> Strings](https://realpython.com/python-strings/)
- [w3schools.org -> Strings](https://www.w3schools.com/python/python_strings.asp)
- [python.org  -> Strings](https://docs.python.org/3/tutorial/introduction.html#strings)