Source code for usgs

__author__ = 'nicksantos'

"""
	Handles all interfacing with USGS, with the goal of making (parts) of their JSON
	API available to Python as native objects
"""

import pandas
import urllib
import urllib2
import json

[docs]class gage():
[docs] def __init__(self, site_code = None, time_period = "P7D", url_params = {}): self.site_code = site_code self.time_series = None self.time_period = time_period self.url_params = url_params # optional dict of params - url key value pairs passed to the api self.data_frame = None self.startDT = None self.endDT = None self._json_string = None self._base_url = "http://waterservices.usgs.gov/nwis/iv/"
[docs] def check_params(self, params = ('site_code',)): """ Makes sure that we have the base level of information necessary to run a query to prevent lazy setup errors """ for param in params: if self.__dict__[param] is None and param not in self.url_params: raise AttributeError("Required attribute %s must be set or provided in url_params before running this method" % param)
[docs] def retrieve(self, return_pandas=False, automerge = True): """ runs the relevant private methods in sequence :param:return_pandas: specifies whether or not to return the pandas object, or to return a standard """ # makes sure that the user didn't forget to set something after init self.check_params() self._retrieve_data() self._json_to_dataframe(create_pandas = return_pandas) if return_pandas: return self.data_frame else: return self.time_series
def _retrieve_data(self): """ requests retrieves, and stores the json """ # add the relevant parameters into the dictionary passed by the user (if any self.url_params['format'] = "json" self.url_params['sites'] = self.site_code if self.time_period and not self.startDT and 'startDT' not in self.url_params: # if we have a time period, but not a time range, use the period self.url_params['period'] = self.time_period else: # otherwise, use the time range if it works (doesn't currently valdidate the dates # TODO: Validate the date formats self.check_params(('startDT','endDT')) # it's possible that they won't be defined self.url_params['startDT'] = self.startDT self.url_params['endDT'] = self.endDT # merge parameters into the url request_url = self._base_url + "?" + urllib.urlencode(self.url_params) # open the url and read in the json string to a private variable request = urllib2.Request(request_url) data_stream = urllib2.urlopen(request) self._json_string = data_stream.read() self._json_data = json.loads(self._json_string) def _json_to_dataframe(self, create_pandas = False): """ converts the json to a pandas data frame """ self.time_series = self._json_data['value']['timeSeries'][0]['values'][0]['value'] if create_pandas: self.data_frame = pandas.DataFrame(self.time_series) def _merge_with_existing(self): """ if we execute a request when we already have data, this method attempts to merge the two datasets into a single time series so you can effectively execute a partial query and then go further if need be """ pass # TODO: Create shortcut function for getting data from a station - single function
def retrieve_flow(user_gage_id=None, return_pandas = False): """ Helper function that initializes the gage for you, runs the necessary methods, and just returns the table. Takes no date limiters so default is used. If you need to specify dates, please use the gage class """ if not user_gage_id: raise ValueError("user_gage_id must be specified to use this helper function. If you want to initialize a gage" "without specifying an ID, please use the gage class") t_gage = gage(user_gage_id) return t_gage.retrieve(return_pandas=return_pandas)