Is Python a

9. Immutable types. Either of the following solutions works. Index assignmentdoesn’t, because strings are immutable:>>> S = "spam">>> S = S[0] + 'l' + S[2:]>>> S'slam'>>> S = S[0] + 'l' + S[2] + S[3]>>> S'slam'10. Nesting. Here is a sample:>>> me = {'name':('mark', 'e', 'lutz'), 'age':'?', 'job':'engineer'}>>> me['job']'engineer'>>> me['name'][2]'lutz'11. Files. Here’s one way to create and read back a text file in Python (ls is a Unixcommand; use dir on Windows):# File: maker.pyfile = open('myfile.txt', 'w')file.write('Hello file world!\n') # Or: open( ).write( )file.close( )# close not always needed# File: reader.pyfile = open('myfile.txt')# 'r' is default open modeprint file.read() # Or print open( ).read( )% python maker.py% python reader.pyHello file world!% ls -l myfile.txt-rwxrwxrwa 1 0 0 19 Apr 13 16:33 myfile.txt12. The dir function revisited. The following is what you get for lists; dictionaries dothe same, with different method names. Note that the dir result expanded inPython 2.2—you’ll see a large set of additional underscore names that implementexpression operators and support the subclassing in Part VI. The _ _methods_ _attribute disappeared in 2.2 as well because it wasn’t consistently implemented—use dir to fetch attribute lists today instead:>>> []._ _methods_ _['append', 'count', 'index', 'insert', 'remove', 'reverse', 'sort',...]>>> dir([])['append', 'count', 'index', 'insert', 'remove', 'reverse', 'sort',...]Part II, Types and Operations | 653