You _can_ just extend a JSON file without loading it, but it will not be "fun".
Say the JSON file contains a top-level array. The final significant character in it would be a ']'. So, you can read just a reasonably-sized block from the end of the file, find the location of the final ']', overwrite it with a ',' followed by your additional array entry/entries, with a final ']'. If the JSON file contains a top-level object, the final significant character would be a '}'. Overwrite it with a ',' followed by your additional object key/value pairs, with a final '}'. Basically, if what you want to append is of the same kind as the content of the file (array appended to array, or object to object): - Locate final significant character in the file - Locate first significant character in your appended data, replace it with a ',' - Overwrite the final significant character in the file with your patched data It isn't elegant or very robust, but if you want to append to a very large JSON array (for example, some log file?), then it could be very efficient and effective. Or, you could use YAML ;-) On Tue, Apr 4, 2017 at 8:31 AM, dieter <die...@handshake.de> wrote: > Dave <dbola...@fastmail.fm> writes: > > > I created a python program that gets data from a user, stores the data > > as a dictionary in a list of dictionaries. When the program quits, it > > saves the data file. My desire is to append the new data to the > > existing data file as is done with purely text files. > > Usually, you cannot do that: > "JSON" stands for "JavaScript Object Notation": it is a text representation > for a single (!) JavaScript object. The concatenation of two > JSON representations is not a valid JSON representation. > Thus, you cannot expect that after such a concatenation, a single > call to "load" will give you back complete information (it might > be that a sequence of "load"s works). > > Personally, I would avoid concatenated JSON representations. > Instead, I would read in (i.e. "load") the existing data, > construct a Python object from the old and the new data (likely in the form > of a list) and then write it out (i.e. "dump") again. > > -- > https://mail.python.org/mailman/listinfo/python-list > -- https://mail.python.org/mailman/listinfo/python-list
