Is Python a

As we have learned, int translates a string of digits into an integer object, and the listcomprehension expression introduced in Chapter 4 can apply the call to each item inour list all at once (you’ll find more on list comprehensions later in this book).Notice that we didn’t have to run rstrip to delete the \n at the end of the last part;int and some other converters quietly ignore whitespace around digits.Finally, to convert the stored list and dictionary in the third line of the file, we canrun them through eval, a built-in function that treats a string as a piece of executableprogram code (technically, a string containing a Python expression):>>> line = F.readline( )>>> line"[1, 2, 3]${'a': 1, 'b': 2}\n">>> parts = line.split('$') # Split (parse) on $>>> parts['[1, 2, 3]', "{'a': 1, 'b': 2}\n"]>>> eval(parts[0]) # Convert to any object type[1, 2, 3]>>> objects = [eval(P) for P in parts] # Do same for all in list>>> objects[[1, 2, 3], {'a': 1, 'b': 2}]Because the end result of all this parsing and converting is a list of normal Pythonobjects instead of strings, we can now apply list and dictionary operations to them inour script.Storing native Python objects with pickleUsing eval to convert from strings to objects, as demonstrated in the preceding code,is a powerful tool. In fact, sometimes it’s too powerful. eval will happily run anyPython expression—even one that might delete all the files on your computer, giventhe necessary permissions! If you really want to store native Python objects, but youcan’t trust the source of the data in the file, Python’s standard library pickle moduleis ideal.The pickle module is an advanced tool that allows us to store almost any Pythonobject in a file directly, with no to- or from-string conversion requirement on ourpart. It’s like a super-general data formatting and parsing utility. To store a dictionaryin a file, for instance, we pickle it directly:>>> F = open('datafile.txt', 'w')>>> import pickle>>> pickle.dump(D, F) # Pickle any object to file>>> F.close( )Then, to get the dictionary back later, we simply use pickle again to recreate it:>>> F = open('datafile.txt')>>> E = pickle.load(F) # Load any object from file>>> E{'a': 1, 'b': 2}180 | Chapter 9: Tuples, Files, and Everything Else