windchillcomp.py

# Column names and column indices to read
columns = {'date':0, 'time':1, 'tempout':2, 'windspeed':7, 'windchill':12}

# Data types for each column (only if non-string)
types = {'tempout': float, 'windspeed':float, 'windchill':float}

# Init. my data variable
data = {}
for column in columns:
    data[column] = []

# Read the data file
filename = "data/wxobs20170821.txt"

with open(filename, 'r') as datafile:  # closes file automatically

    # read the first 3 lines (header)
    for _ in range(3):
        datafile.readline()

    # read and parse the rest of the file
    for line in datafile:
        split_line = line.split()  # () splits whitespace
        for column in columns:
            i = columns[column]
            t = types.get(column, str)
            value = t(split_line[i])
            data[column].append(value)

# Compute the wind chill temperature
def compute_windchill(t, v):
    a = 35.74  # empirical constants
    b = 0.6215  # this formula fits best for temp < 45 F
    c = 35.75
    d = 0.4275

    v16 = v ** 0.16

    wci = a + b * t - c * v16 + d * t * v16

    return wci

# Running the function to compute wci
windchill = []
for temp, windspeed in zip(data['tempout'], data['windspeed']):
    windchill.append(compute_windchill(temp, windspeed))

# Output comparison of data
print('                ORIGINAL  COMPUTED')
print(' DATE    TIME  WINDCHILL WINDCHILL DIFFERENCE')
print('------- ------ --------- --------- ----------')
zip_data = zip(data['date'], data['time'], data['windchill'], windchill)
for date, time, wc_orig, wc_comp in zip_data:
    wc_diff = wc_orig - wc_comp
    print(f'{date} {time:>6} {wc_orig:9.6f} {wc_comp:9.6f} {wc_diff:10.6f}')