while True:
my_dict={}
b = box.tolist()
t = np.array(timestamp).tolist()
my_dict["coordinates"] = b
my_dict["timestamp"]= t
all_dict.append(my_dict)
for my_dict in all_dict:
with open("co.json", 'a') as fp:
json.dump(my_dict,fp)
Output needs to be as json format, but it is not like this { {},{},{} }, it has just dump as {}{}{} without comma separator and without outer {}
that's because you're dumping each sub-directory as if it was separate single dictionaries. So it doesn't write the wrapping braces nor the commas.
Instead, don't loop on the sub-dicts, just dump the whole list of dicts (adding indent parameter allows to "prettyprint" the dump if needed):
with open("co.json", 'w') as fp:
json.dump(all_dict,fp,indent=2)
(you don't need append mode either now, just open for writing/truncating)
Note that you won't get a "dict" of dicts but a list of dicts as a result: like [ {a:b}, {c:d} ], which is also valid json.
with open("coordinates.json", 'w') as fp:
fp.write('{')
for my_dict in all_dict:
if (my_dict!=all_dict[-1]):
#fp.write('"key":'+json.dumps(my_dict)+',\n')
else:
fp.write('"key":'+json.dumps(my_dict))
fp.write('}')
