Python Substrings

Unlike a C string, Python strings cannot be changed. Assigning to an indexed position in the string results in an error. An Informal Introduction To Python

"Hello World!"[0]     # Returns 'H'
"Hello World!"[1]     # Returns 'e'
"Hello World!"[5]     # Returns ' '
"Hello World!"[6]     # Returns 'W'
"Hello World!"[11]    # Returns '!'
"Hello World!"[12]    # Causes IndexError: string index out of range

"Hello World!"[-1]    # Returns '!'
"Hello World!"[-2]    # Returns 'd'
"Hello World!"[-6]    # Returns 'W'
"Hello World!"[-7]    # Returns ' '
"Hello World!"[-11]   # Returns 'e'
"Hello World!"[-12]   # Returns 'H'
"Hello World!"[-13]   # Causes IndexError: string index out of range

"Hello World!"[0:2]   # Returns 'He'
"Hello World!"[1:5]   # Returns 'ello'
"Hello World!"[5:1]   # Returns ''
"Hello World!"[3:]    # Returns 'lo World!'
"Hello World!"[:4]    # Returns 'Hell'

"Hello World!"[-5:-3] # Returns 'or'
"Hello World!"[-5:]   # Returns 'orld!'
"Hello World!"[:-4]   # Returns 'Hello Wo'