app.py

#################################### AN APP.PY file
#DEPENDENCIES
###############################################
import datetime as dt
import numpy as np
import pandas as pd

import sqlalchemy
from sqlalchemy.ext.automap import automap_base
from sqlalchemy.orm import Session
from sqlalchemy import create_engine, func

from flask import Flask, jsonify

#################################################
# Database Setup
#################################################
engine = create_engine("sqlite:///hawaii.sqlite")

# reflect an existing database into a new model
Base = automap_base()
# reflect the tables
Base.prepare(engine, reflect=True)

# Save references to each table
Measurement = Base.classes.measurement
Station = Base.classes.station

# Create our session (link) from Python to the DB
session = Session(engine)

#################################################
# Flask Setup
#################################################
app = Flask(__name__)


#################################################
# FLASK ROUTES 
#################################################

@app.route("/")
def welcome():
    return (
        f"Welcome to the Climate Analysis API!<br/>"
        f"Available Routes:<br/>"
        f"/api/v1.0/precipitation<br/>"
        f"/api/v1.0/stations<br/>"
        f"/api/v1.0/tobs<br/>"
        f"/api/v1.0/temp/start/end"
    )


@app.route("/api/v1.0/precipitation")
def precipitation():
   prev_year = dt.date(2017, 8, 23) - dt.timedelta(days=365)
   precipitation = session.query(Measurement.date, Measurement.prcp).\
    filter(Measurement.date >= prev_year).all()
   precip = {date: prcp for date, prcp in precipitation}
   session.close()
   return jsonify(precip)
 

@app.route("/api/v1.0/stations")
def stations():
    results = session.query(Station.station).all()
    stations = list(np.ravel(results))
    session.close()
    return jsonify(stations=stations)

@app.route("/api/v1.0/tobs")
def temp_monthly():
    #Return the temperature observations (tobs) for previous year.
    # Calculate the date 1 year ago from last date in database
    prev_year = dt.date(2017, 8, 23) - dt.timedelta(days=365)

    # Query the primary station for all tobs from the last year
    results = session.query(Measurement.tobs).\
        filter(Measurement.station == 'USC00519281').\
        filter(Measurement.date >= prev_year).all()

    # Unravel results into a 1D array and convert to a list
    temps = list(np.ravel(results))
    session.close()
    # Return the results
    return jsonify(temps)


@app.route("/api/v1.0/temp/<start>")
@app.route("/api/v1.0/temp/<start>/<end>")
def stats(start=None, end=None):
    ##Return TMIN, TAVG, TMAX.

    # Select statement
    sel = [func.min(Measurement.tobs), func.avg(Measurement.tobs), func.max(Measurement.tobs)]
    print ("=============")
    print (start)
    print (end)
    print ("=============")
    if not end:
        # calculate TMIN, TAVG, TMAX for dates greater than start
        results = session.query(*sel).\
            filter(Measurement.date >= start).all()
        # Unravel results into a 1D array and convert to a list
        temps = list(np.ravel(results))
        session.close()
        return jsonify(temps)

    # calculate TMIN, TAVG, TMAX with start and stop
    results = session.query(*sel).\
        filter(Measurement.date >= start).\
        filter(Measurement.date <= end).all()
    # Unravel results into a 1D array and convert to a list
    temps = list(np.ravel(results))
    session.close()
    return jsonify(temps)

if __name__ == '__main__':
    app.run(debug=True)