Replace null values in Json file

[buran]

I replied to but nobody listens Doh
:-)

[burnsssss]

Sorry again,
i proved the code and when i try read the json generated, now give me error message:

with open("CON_ERROR_LUNES.json", "r") as f:
    data = json.load(f)

ValueError: Extra data: line 2 column 1 - line 6 column 1 (char 6214 - 27304)

The file has the next shape:

{"created_at":"Mon Jun 11 09:31:04 +0000 2018","id":1006106533749501957,"id_str":"1006106533749501957","text":"Mi cr\u00edtica para @Codalario de \u201cLa tabernera del puerto\u201d del Teatro Campoamor https:\/\/t.co\/xnoRsAJKZy","display_text_range":[0,76],"source":"\u003ca href=\"http:\/\/twitter.com\/download\/iphone\" rel=\"nofollow\"\u003eTwitter for iPhone\u003c\/a\u003e","truncated":false,"in_reply_to_status_id":null,"in_reply_to_status_id_str":null,"in_reply_to_user_id":null,"in_reply_to_user_id_str":null,"in_reply_to_screen_name":null,"user":{"id":159561704,"id_str":"159561704","name":"Nuria Blanco \u00c1lvarez","screen_name":"miladomusical","location":null,"url":null,"description":"Music\u00f3loga. Cr\u00edtico musical en Scherzo y Codalario. Adoro la zarzuela. Profesora por vocaci\u00f3n.","translator_type":"none","protected":false,"verified":false,"followers_count":224,"friends_count":74,"listed_count":11,"favourites_count":996,"statuses_count":1386,"created_at":"Fri Jun 25 18:39:22 +0000 2010","utc_offset":null,"time_zone":null,"geo_enabled":true,"lang":"es","contributors_enabled":false,"is_translator":false,"profile_background_color":"642D8B","profile_background_image_url":"http:\/\/abs.twimg.com\/images\/themes\/theme10\/bg.gif","profile_background_image_url_https":"https:\/\/abs.twimg.com\/images\/themes\/theme10\/bg.gif","profile_background_tile":true,"profile_link_color":"FF0000","profile_sidebar_border_color":"65B0DA","profile_sidebar_fill_color":"7AC3EE","profile_text_color":"3D1957","profile_use_background_image":true,"profile_image_url":"http:\/\/pbs.twimg.com\/profile_images\/775392431705579520\/30Kwq6si_normal.jpg","profile_image_url_https":"https:\/\/pbs.twimg.com\/profile_images\/775392431705579520\/30Kwq6si_normal.jpg","profile_banner_url":"https:\/\/pbs.twimg.com\/profile_banners\/159561704\/1448747141","default_profile":false,"default_profile_image":false,"following":null,"follow_request_sent":null,"notifications":null},"geo":null,"coordinates":null,"place":null,"contributors":null....

I think im lost some of json files...

When i read the file, i will use replace_nulls function for replace None and next i will save the new json dict file generated. But i dont understand because i cannot read the file when 5 minutes ago i can read other file of tweets.
Thank you very much and sorry again