Operations on Strings

Concatenation (+ and *)





  



 (ch08_add) 












Indexing with ([])


The indexing operator selects a single character from a string.

index values

It is also the case that the positions are named from right to left using negative numbers where -1 is the rightmost index and so on.



































  



 (chp08_index1) 












For loop traversal (for)


Traversing a string means accessing each character in the string, one at a time.  For example, the following for loop:


for ix in 'Example':
...





executes the body of the loop 7 times with different values of ix each time.






Length


The len function, when applied to a string, returns the number of characters in a string.
Example: len('happy') evaluates to 5.



































  



 (chp08_len2) 












Slice


A substring of a string is called a slice. The slice operator [n:m] returns the part of the string from the n’th character
to the m’th character, including the first but excluding the last.



































  



 (chp08_slice1) 












String Comparison (>, <, >=, <=, ==, !=)


The six common comparision operators work with strings, evaluating according to lexigraphical order.
Examples:


    

  • 'apple' < 'banana' evaluates to True.
    • 

  • 'Zeta' < 'Appricot' evaluates to False.
    • 

  • 'Zebra' <= 'aardvark' evaluates to True because all upper case letters precede lower case letters.
    • 







in and not in operator (in, not in)


The in operator tests whether one string is contained inside another string.
Examples:


    

  • 'heck' in "I'll be checking for you." evaluates to True.
    • 

  • 'cheese' in "I'll be checking for you." evaluates to False.
    • 




































  



 (chp08_slice1) 













  
      
  
  
  
  
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