Page 169 -

persistence

Save with dump and restore with load

Using pickle is straightforward: import the required module, then use
dump() to save your data and, some time later, load() to restore it. The
only requirement when working with pickled files is that they have to be
opened in binary access mode:

Always import pickle
remember ...
to import
the “pickle” with open('mydata.pickle', 'wb') as mysavedata: The “b” tells
module. pickle.dump([1, 2, 'three'], mysavedata) Python to open
T o save your data, ... your data files
use “dump()”. with open('mydata.pickle', 'rb') as myrestoredata: in BINARY
mode.
a_list = pickle.load(myrestoredata)
Assign your
restored data print(a_list) file using “load()”.
Restore your data from your
to an identifier.

Once your data is back in your program, you can
treat it like any other data object.

What if something goes wrong?

If something goes wrong when pickling or unpickling your data, the pickle
module raises an exception of type PickleError.

w Here’s a snippet of your code as it currently stands. Grab your
pencil and strike out the code you no longer need, and then
replace it with code that uses the facilities of pickle instead.
Add any additional code that you think you might need, too.

try:
with open('man_data.txt', 'w') as man_file, open('other_data.txt', 'w') as other_file:
nester.print_lol(man, fh=man_file)
nester.print_lol(other, fh=other_file)
except IOError as err:
print('File error: ' + str(err))

you are here 4 133