String functions and methods (len, upper, lower)

• len
• upper
• lower

a = "xYz"
print(len(a))     # 3

b = a.upper()
print(b)          # XYZ
print(a)          # xYz   - immutable!
print(a.lower())  # xyz

• Type dir("") in the REPL to get the list of string methods.
• List of built-in functions.
• List of string methods.