import json

foo = {}

for i in range(1000):
    json.dumps(foo)
    print(i)
    foo = {'bar': foo}


Will error at 994. At a minimum this magic number should be documented, but it would be better if the json library could handle arbitrarily nested JSON or have a configurable limit.

https://github.com/lovasoa/bad_json_parsers

There is nothing here specific to JSON.  It is Python's normal (and documented) limit on recursion. 

If needed, you can change the limit to as large as needed:

    import json
    import sys
    sys.setrecursionlimit(50_000)

    foo = {}

    for i in range(10_000):
        foo = {'bar': foo}
    s = json.dumps(foo)
    print(len(s))