in jupyter notebook, I ran this code in a cell:
for i in range(10):
with open('data.json', 'w') as f:
json.dump({"counter":i}, f)
time.sleep(10000)
easy so far, but after executing the cell there won't be any update on the actual data.json file during each iteration, it will get updated up until the end of the program. in other words, the data.json as a file object stays open till the end of the code.
how can I update the file on the disk in a loop?
The json module doesn't work that way AFAIK. You'll have to load the json data into a dictionary/list then make your changes, then write the file again:
# funciton to read json files
def read_json(path):
with open(path, 'r') as file:
return json.load(file)
# function to write json files
def write_json(path, data, indent=4):
with open(path, 'w') as file:
json.dump(data, file, indent=indent)
# read some json data
json_data = read_json('./my_json_file.json')
# ... do some stuff to the data
# write the data back to the file
write_json('./my_json_file.json', json_data)
Related
I want to write data to a json file. If it does not exists, I want to create that file, and write data to it. I wrote code for it, but I'm getting json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0).
Here's part of my code:
data = {"foo": "1"}
with open("file.json", "w+") as f:
try:
file_data = json.load(f)
json.dump(data, f)
print("got data from file:", file_data)
except json.decoder.JSONDecodeError:
json.dump(data, f)
print("wrote")
I put print statements so that I can "track" what's going on, but If I try to run this code multiple times, I keep getting wrote message.
Thanks in advance for help!
The problem is that you open the file for write/read therefore once you open the file it will be emptied.
Then you want to load the content with json.load and it obviously fails because the file is not a valid JSON anymore.
So I'd suggest to open the file for reading and writing separately:
import json
with open("file.json") as json_file:
file_data = json.load(json_file)
print("got data from file:", file_data)
data = {"foo": "1"}
with open("file.json", "w") as json_file:
json.dump(data, json_file)
Hope it helps!
Scenario is i need to convert dictionary object as json and write to a file . New Dictionary objects would be sent on every write_to_file() method call and i have to append Json to the file .Following is the code
def write_to_file(self, dict=None):
f = open("/Users/xyz/Desktop/file.json", "w+")
if json.load(f)!= None:
data = json.load(f)
data.update(dict)
f = open("/Users/xyz/Desktop/file.json", "w+")
f.write(json.dumps(data))
else:
f = open("/Users/xyz/Desktop/file.json", "w+")
f.write(json.dumps(dict)
Getting this error "No JSON object could be decoded" and Json is not written to the file. Can anyone help ?
this looks overcomplex and highly buggy. Opening the file several times, in w+ mode, and reading it twice won't get you nowhere but will create an empty file that json won't be able to read.
I would test if the file exists, if so I'm reading it (else create an empty dict).
this default None argument makes no sense. You have to pass a dictionary or the update method won't work. Well, we can skip the update if the object is "falsy".
don't use dict as a variable name
in the end, overwrite the file with a new version of your data (w+ and r+ should be reserved to fixed size/binary files, not text/json/xml files)
Like this:
def write_to_file(self, new_data=None):
# define filename to avoid copy/paste
filename = "/Users/xyz/Desktop/file.json"
data = {} # in case the file doesn't exist yet
if os.path.exists(filename):
with open(filename) as f:
data = json.load(f)
# update data with new_data if non-None/empty
if new_data:
data.update(new_data)
# write the updated dictionary, create file if
# didn't exist
with open(filename,"w") as f:
json.dump(data,f)
Is there a way to append single JSON objects to a json file while in a for loop in python. I would prefer not store all my data in one giant json object and dump it all at once, as I am planning on performing millions of API requests. I would like to make a single API request, dump the result into a JSON file and then move to the next API request and dump that into the same JSON file.
The below code overwrites the JSON file, I am looking for something that appends.
for url in urls:
r = sesh.get(url)
data = r.json()
with open('data.json', 'w') as outfile:
json.dump(data, outfile)
Such that:
with open('data.json') as outfile:
data = json.load(data, outfile)
type(data)
>> dict
r.json looks something like this:
{'attribute1':1, 'attribute2':10}
Update
Well since I don't have access to your API I just placed some sample responses, in the format you supplied, inside an array.
import json
urls = ['{"attribute1":1, "attribute2":10}', '{"attribute1":67, "attribute2":32}', '{"attribute1":37, "attribute2":12}'];
json_arr = []
for url in urls:
data = json.loads(url)
json_arr.append(data)
with open('data.json', 'w') as outfile:
json.dump(json_arr, outfile)
Basically we keep an array and append each API response to that array. Then, we can write the accumulative JSON to a file. Also if you want to update the same JSON file on different executions of the code, you can just read the existing output file into an array, in the beginning of the code, and then carry on with my example.
Change write mode to append
Try changing this:
with open('data.json', 'w') as outfile:
To this:
with open('data.json', 'a') as outfile:
The previous answer is surprisingly close to what you need to do.
So I will build upon it.
import json
json_arr = ['{"attribute1":1, "attribute2":10}', '{"attribute1":67, "attribute2":32}', '{"attribute1":37, "attribute2":12}'];
with open('data.json', 'w') as outfile:
outfile.write('[')
for element in json_arr:
with open('data.json', 'w') as outfile:
json.dump(element, outfile)
outfile.write(',')
with open('data.json', 'a') as outfile:
outfile.write(']')
I used this tweepy-based code to pull the tweets of a given user by user_id. I then saved a list of all tweets of a given user (alltweets) to a json file as follows. Note that without "repr", i wasn't able to dump the alltweets list into json file. The code worked as expected
with open(os.path.join(output_file_path,'%s_tweets.json' % user_id), 'a') as f:
json.dump(repr(alltweets), f)
However, I have a side problem with retrieving the tweets after saving them to the json file. I need to access the text in each tweet, but I'm not sure how to deal with the "Status" wrapper that tweepy uses (See a sample of the json file attached).sample json file content
I tried to iterate over the lines in the file as follows, but the file is being seen as a single line.
with open(fname, 'r') as f:
for line in f:
tweet = json.loads(line)
I also tried to iterate over statuses after reading the json file as a string, as follows, but iteration rather takes place on the individual characters in the json file.
with open(fname, 'r') as f:
x = f.read()
for status in x:
"""code"""
Maybe not the prettiest solution but you could just declare Status as a dict and then eval the list (the whole content of the files).
Status = dict
f = open(fname, 'r')
data = eval(f.read())
f.close()
for status in data:
""" do your stuff"""
I am using Blair's Python script which modifies a CSV file to add the filename as the last column (script appended below). However, instead of adding the file name alone, I also get the Path and File name in the last column.
I run the below script in windows 7 cmd with the following command:
python C:\data\set1\subseta\add_filename.py C:\data\set1\subseta\20100815.csv
The resulting ID field is populated by the following C:\data\set1\subseta\20100815.csv, although, all I need is 20100815.csv.
I'm new to python so any suggestion is appreciated!
import csv
import sys
def process_file(filename):
# Read the contents of the file into a list of lines.
f = open(filename, 'r')
contents = f.readlines()
f.close()
# Use a CSV reader to parse the contents.
reader = csv.reader(contents)
# Open the output and create a CSV writer for it.
f = open(filename, 'wb')
writer = csv.writer(f)
# Process the header.
header = reader.next()
header.append('ID')
writer.writerow(header)
# Process each row of the body.
for row in reader:
row.append(filename)
writer.writerow(row)
# Close the file and we're done.
f.close()
# Run the function on all command-line arguments. Note that this does no
# checking for things such as file existence or permissions.
map(process_file, sys.argv[1:])
Use os.path.basename(filename). See http://docs.python.org/library/os.path.html for more details.