Python pickle/unpickle a list to/from a file

Question

I have a list that looks like this:

a = [['a string', [0, 0, 0], [22, 'bee sting']], ['see string',      [0, 2, 0], [22, 'd string']]] 

and am having problems saving it and retrieving it.

I can save it ok using pickle:

with open('afile','w') as f:     pickle.dump(a,f) 

but get the following error when I try to load it:

pickle.load('afile')  Traceback (most recent call last):   File "<pyshell#116>", line 1, in <module>     pickle.load('afile')   File "C:\Python27\lib\pickle.py", line 1378, in load     return Unpickler(file).load()   File "C:\Python27\lib\pickle.py", line 841, in __init__     self.readline = file.readline AttributeError: 'str' object has no attribute 'readline' 

I had thought that I could convert to a numpy array and use save, savez or savetxt. However I get the following error:

>>> np.array([a])  Traceback (most recent call last):   File "<pyshell#122>", line 1, in <module>     np.array([a]) ValueError: cannot set an array element with a sequence 

Answer 1

Decided to make it as an answer. pickle.load method expects to get a file like object, but you are providing a string instead, and therefore an exception. So instead of:

pickle.load('afile') 

you should do:

pickle.load(open('afile', 'rb'))