CODEWITHSUNDEEP
pythonsqlitetuples
Ben Jones
Ben Jones

Reputation: 525

Do something different on last row of a tuple

I'm manually constructing a JSON so I want the last element to not have a , seperator before the ].

This my code and the documentation says len() works for tuples but I can't get it to work. The data is a tuple constructed from a SQLite.fetchall() and it has been validated.

for row in data: 
    f.write("{\n")
    f.write(f"'PUT':'{row[1]}'\n")
    if row == len(data):  # I also tried len(data)-1 as suggested by posts
        f.write("}\n")
    else:
        f.write("},\n")

This code constructs the JSON but all elements including the last have the , separator.

What is the best pythonic way to do this?

Upvotes: -1

Views: 104

Answers (2)

C.Nivs
C.Nivs

Reputation: 13106

Use a str.join to help you format the records, that will get all except the last one, and you can concatenate on the \n to the last record:

# concatenate the last `\n` onto the end after joining
records = ',\n'.join(
    "{\n'PUT':'{value}'\n}".format(value=row[1])
    for row in data
) + '\n'

with open(file) as fh:
    fh.write(records)

Edit

Since it looks like you are trying to roll your own in terms of json encoding, don't. You can make this easier by doing:

import json

records = ',\n'.join(
    (json.dumps({"PUT": row[1]}, indent=0), for row in data)
) + '\n'

Where the indent=0 kwarg will insert the newlines you want:

# compare the two
json.dumps({"some": "value"}, indent=0)
'{\n"some": "value"\n}'

json.dumps({"some": "value"})
'{"some": "value"}'

Upvotes: 1

Ben Jones
Ben Jones

Reputation: 525

Solved it

if row == data[len(data)-1]:
    f.write("}\n")
else:
    f.write("},\n")

Upvotes: 0

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