I prefer

  >> import json, decimal
  >> j = "47234762761726473624762746721647624764380000000000000000000000000000000000000000000"
  >> json.loads(j, parse_float=decimal.Decimal, parse_int=decimal.Decimal)
  Decimal('47234762761726473624762746721647624764380000000000000000000000000000000000000000000')

This way you avoid this problem:

  >> import json
  >> j = "0.47234762761726473624762746721647624764380000000000000000000000000000000000000000000"
  >> json.loads(j)
  0.47234762761726473

And instead can get:

  >> import json, decimal
  >> j = "0.47234762761726473624762746721647624764380000000000000000000000000000000000000000000"
  >> json.loads(j, parse_float=decimal.Decimal, parse_int=decimal.Decimal)
  Decimal('0.47234762761726473624762746721647624764380000000000000000000000000000000000000000000')