CODEWITHSUNDEEP
pythonpython-3.xpickle
John Rowland
John Rowland

Reputation: 3619

Using pickle.dump - TypeError: must be str, not bytes

I'm using python3.3 and I'm having a cryptic error when trying to pickle a simple dictionary.

Here is the code:

import os
import pickle
from pickle import *
os.chdir('c:/Python26/progfiles/')

def storvars(vdict):      
    f = open('varstor.txt','w')
    pickle.dump(vdict,f,)
    f.close()
    return

mydict = {'name':'john','gender':'male','age':'45'}
storvars(mydict)

and I get:

Traceback (most recent call last):
  File "C:/Python26/test18.py", line 31, in <module>
    storvars(mydict)
  File "C:/Python26/test18.py", line 14, in storvars
    pickle.dump(vdict,f,)
TypeError: must be str, not bytes

Upvotes: 344

Views: 149789

Answers (3)

Xinzhe Li
Xinzhe Li

Reputation: 382

pickle uses a binary protocol, hence only accepts binary files. As the document said in the first sentence, "The pickle module implements binary protocols for serializing and de-serializing".

Upvotes: 0

Well Smith
Well Smith

Reputation: 791

Just had same issue. In Python 3, Binary modes 'wb', 'rb' must be specified whereas in Python 2x, they are not needed. When you follow tutorials that are based on Python 2x, that's why you are here. 

import pickle

class MyUser(object):
    def __init__(self,name):
        self.name = name

user = MyUser('Peter')

print("Before serialization: ")
print(user.name)
print("------------")
serialized = pickle.dumps(user)
filename = 'serialized.native'

with open(filename,'wb') as file_object:
    file_object.write(serialized)

with open(filename,'rb') as file_object:
    raw_data = file_object.read()

deserialized = pickle.loads(raw_data)


print("Loading from serialized file: ")
user2 = deserialized
print(user2.name)
print("------------")

Upvotes: 44

Jon Clements
Jon Clements

Reputation: 142146

The output file needs to be opened in binary mode:

f = open('varstor.txt','w')

needs to be:

f = open('varstor.txt','wb')

Upvotes: 565

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