python – How can I use pickle to save a dict?

python – How can I use pickle to save a dict?

Try this:

import pickle

a = {hello: world}

with open(filename.pickle, wb) as handle:
    pickle.dump(a, handle, protocol=pickle.HIGHEST_PROTOCOL)

with open(filename.pickle, rb) as handle:
    b = pickle.load(handle)

print a == b

import pickle

your_data = {foo: bar}

# Store data (serialize)
with open(filename.pickle, wb) as handle:
    pickle.dump(your_data, handle, protocol=pickle.HIGHEST_PROTOCOL)

# Load data (deserialize)
with open(filename.pickle, rb) as handle:
    unserialized_data = pickle.load(handle)

print(your_data == unserialized_data)

The advantage of HIGHEST_PROTOCOL is that files get smaller. This makes unpickling sometimes much faster.

Important notice: The maximum file size of pickle is about 2GB.

Alternative way

import mpu
your_data = {foo: bar}
mpu.io.write(filename.pickle, data)
unserialized_data = mpu.io.read(filename.pickle)

Alternative Formats

• CSV: Super simple format (read & write)
• JSON: Nice for writing human-readable data; VERY commonly used (read & write)
• YAML: YAML is a superset of JSON, but easier to read (read & write, comparison of JSON and YAML)
• pickle: A Python serialization format (read & write)
• MessagePack (Python package): More compact representation (read & write)
• HDF5 (Python package): Nice for matrices (read & write)
• XML: exists too *sigh* (read & write)

For your application, the following might be important:

• Support by other programming languages
• Reading / writing performance
• Compactness (file size)

See also: Comparison of data serialization formats

In case you are rather looking for a way to make configuration files, you might want to read my short article Configuration files in Python

python – How can I use pickle to save a dict?

# Save a dictionary into a pickle file.
import pickle

favorite_color = {lion: yellow, kitty: red}  # create a dictionary
pickle.dump(favorite_color, open(save.p, wb))  # save it into a file named save.p

# -------------------------------------------------------------
# Load the dictionary back from the pickle file.
import pickle

favorite_color = pickle.load(open(save.p, rb))
# favorite_color is now {lion: yellow, kitty: red}