{"id":585,"date":"2017-01-21T16:04:40","date_gmt":"2017-01-21T08:04:40","guid":{"rendered":"https:\/\/www.techcoil.com\/blog\/?p=585"},"modified":"2018-09-05T00:19:28","modified_gmt":"2018-09-04T16:19:28","slug":"how-to-save-and-load-objects-to-and-from-file-in-python-via-facilities-from-the-pickle-module","status":"publish","type":"post","link":"https:\/\/www.techcoil.com\/blog\/how-to-save-and-load-objects-to-and-from-file-in-python-via-facilities-from-the-pickle-module\/","title":{"rendered":"How to save and load objects to and from file in Python via facilities from the pickle module"},"content":{"rendered":"

There are times when it is more convenient for us to choose object serialization over database management systems for the persistency of the data that our Python scripts work with. <\/p>\n

In this post, I document how we can save and load objects to and from file in Python using facilities from the pickle module.<\/p>\n

Saving objects to file in Python<\/h2>\n

To save objects to file in Python, we typically go through the following steps:<\/p>\n

    \n
  1. Import the pickle module<\/a>.<\/li>\n
  2. Get a file handle in write mode that points to a file path.<\/li>\n
  3. Use pickle.dump<\/code><\/a> to write the object that we want to save to file via that file handle.<\/li>\n<\/ol>\n

    With these steps in mind, let's us create a Python script, save_dictionary_to_file.py<\/code>, with the following Python codes:<\/p>\n

    \r\n# Step 1\r\nimport pickle\r\n\r\nconfig_dictionary = {'remote_hostname': 'google.com', 'remote_port': 80}\r\n\r\n# Step 2\r\nwith open('config.dictionary', 'wb') as config_dictionary_file:\r\n\r\n  # Step 3\r\n  pickle.dump(config_dictionary, config_dictionary_file)\r\n<\/pre>\n
    In step 1, we import the pickle module with the import<\/code> keyword. <\/p>\n
    In step 2, we use the with<\/code> keyword and the open<\/a> function to create a file handle that points to config.dictionary<\/code> in the same directory where we will run save_dictionary_to_file.py<\/code>. <\/p>\n
    The first string that we supply to the open<\/code> function denotes the filepath to write our dictionary of values. The second string that we supply to the open function indicates that we want a file handle that writes binary contents to the file.<\/p>\n
    The with<\/code> keyword ensures that the file handle generated by the open<\/code> function is closed after our dictionary is serialized to file.<\/p>\n
    Finally in step 3, we use the pickle.dump<\/code><\/a> function to write the contents of our dictionary to a file that will be named as config.dictionary<\/code>.<\/p>\n
    After running save_dictionary_to_file.py<\/code>, we should be able to see the config.dictionary file in the same directory where we run our Python script. <\/p>\n
    Loading objects from file in Python<\/h2>\n
    To load the object from file in Python, we typically go through the following steps:<\/p>\n
      \n
    1. Import the pickle module<\/a>.<\/li>\n
    2. Get a file handle in read mode that points to a file path that has a file that contains the serialized form of a Python object.<\/li>\n
    3. Use pickle.load<\/code><\/a> to read the object from the file that contains the serialized form of a Python object via the file handle.<\/li>\n<\/ol>\n
      With these steps in mind, let us create a Python script, load_dictionary_from_file.py<\/code> with the following Python codes:<\/p>\n
      \r\n# Step 1\r\nimport pickle\r\n\r\n# Step 2\r\nwith open('config.dictionary', 'rb') as config_dictionary_file:\r\n\r\n    # Step 3\r\n    config_dictionary = pickle.load(config_dictionary_file)\r\n\r\n    # After config_dictionary is read from file\r\n    print(config_dictionary)\r\n<\/pre>\n
      Similar to writing the dictionary to file, we import the pickle module in step 1.<\/p>\n
      In step 2, we use the with<\/code> keyword with the open function to get a file handle that points to config.dictionary<\/code> in the same directory where we will run load_dictionary_from_file.py<\/code>. <\/p>\n
      As with saving the dictionary to file, we supply config.dictionary<\/code> as the first input to the open<\/code> function to indicate the file path to the file which contains the serialized dictionary. This time round, we supply the string 'rb'<\/strong> instead of 'wb'<\/strong> to indicate that we want a file handle that reads binary contents from the file. <\/p>\n
      Finally in step 3, we load the dictionary from the file to the config_dictionary variable via the pickle.load<\/code><\/a> function.<\/p>\n
      Once we had loaded the dictionary from the file to the config_dictionary<\/code> variable, we use the print<\/code><\/a> function to print the dictionary contents to the standard output.<\/p>\n\n