Read-only File System: 'data.json': IOError In Aws Lambda Function

I am trying to read data from PDF stored in S3 bucket, convert it to text and then dump these text into json file.

Finally I want to upload this json file to elastic search for indexing.

I have written below code snippet for doing this:

with open('data.json','w') as f:
        json.dump(doc,f)
        dataj=json.load(f)
        doc_data=dataj[:]

doc is the text which I have extracted using pdfminer. when executing this code I'm getting below error.

[Errno 30] Read-only file system: 'data.json': IOError
Traceback (most recent call last):
File "/var/task/lambda_function.py", line 56, in lambda_handler
raise e
IOError: [Errno 30] Read-only file system: 'data.json'.

Someone please help me in finding what I'm doing wrong here.

You're trying to write a file where is not permitted.

Lambda currently only supports writing files to the /tmp directory.

with open('/tmp/data.json','w') as f:
        json.dump(doc,f)
        dataj=json.load(f)
        doc_data=dataj[:]