numbers_from_file

# Reads a CSV file containg weather data of the HISTALP project,
# see http://www.zamg.ac.at/histalp/dataset/station/csv.php
# Copyright 2022, 2023 Roland Richter                     [Mu: Python 3]


def read_histalp_meta(file_name):
    """Read a file in HISTALP format, and return a dictionary with meta data

    Example:
    hist_meta = read_histalp_meta("HISTALP_AT_LIN_T01_1816_2022.csv")
    hist_sttn = hist_meta['station']   # name of station is Linz

    Arguments:
    file_name -- the name of the HISTALP file
    """
    csv_file = open(file_name, 'r')
    hist_meta = {}

    for csv_line in csv_file:
        # In HISTALP CSV files, a line starting with a '#' character is a comment;
        # such lines starting may contain "key: value" entries, e.g.
        # "# parameter: Mean temperature"
        # "# source: http://www.zamg.ac.at/histalp"
        # "# station: Linz-Stadt"
        if csv_line.startswith('#'):
            # The first ':' character always separates key from value; however,
            # some values might contain the ':' character as well, as in
            # "# source: http://www.zamg.ac.at/histalp"
            # Hence, split into *at most* two parts: first the key, second the value.
            csv_entries = csv_line[1:].split(':', 1)
            if len(csv_entries) == 2:
                key = csv_entries[0].strip()
                hist_meta[key] = csv_entries[1].strip()
        else:
            pass

    csv_file.close()
    return hist_meta


def read_histalp_data(file_name, factor=1.0):
    """Read a file in HISTALP format, and return a dictionary (keys: 1815, 2022,
        ...) of dictionaries (keys: 'jan', 'feb', ...).

    Example:
    hist_data = read_histalp_data("HISTALP_AT_LIN_T01_1816_2022.csv")
    mean_tmpr = hist_data[1974]['mar']   # mean temperature of March 1974

    Arguments:
    file_name -- the name of the HISTALP file
    factor -- number to multiply all values with; only necessary for temperature (0.1)
    """
    csv_file = open(file_name, 'r')
    hist_data = {}
    is_first_line = True

    for csv_line in csv_file:
        # ignore all lines starting with a '#' character, as these are comments
        if csv_line.startswith('#'):
            pass
        else:
            csv_entries = csv_line.strip().split(';')
            # the first non-comment line contains the column headers
            if is_first_line:
                column_header = csv_entries
                is_first_line = False
            else:
                year = int(csv_entries[0])
                year_dict = {}
                # go through all entries of a line (except the first);
                # store the value (multiplied with the factor),
                # or 'nan' ('not a number') to indicate missing values
                for k in range(1, len(csv_entries)):
                    entry = csv_entries[k]
                    header = column_header[k]
                    if entry != "999999":
                        year_dict[header] = factor * float(entry)
                    else:
                        year_dict[header] = "nan"

                hist_data[year] = year_dict

    csv_file.close()
    return hist_data


name = "HISTALP_AT_LIN_T01_1816_2022.csv"   # Mean temperature
# name = "HISTALP_AT_LIN_R01_1852_2022.csv"   # Precipitation Totals

histalp_meta = read_histalp_meta(name)
print(histalp_meta)

# Temperate data is given in units of 0,1 °C; convert it to ordinary °C
if histalp_meta["unit"].startswith("0,1"):
    histalp_data = read_histalp_data(name, 0.1)
    histalp_meta["unit"] = "°C"
else:
    histalp_data = read_histalp_data(name)

print("Data available for", histalp_data.keys())
year = int(input("Which year are you interested in? "))

if year not in histalp_data:
    print("Sorry, no data for", year)
else:
    print("Year", year, "has entries for", histalp_data[year].keys())
    month = input("Which month or period are you interested in? ")

    if month not in histalp_data[year]:
        print("Sorry, no data for", month, year)
    else:
        param = histalp_meta["parameter"]
        statn = histalp_meta["station"]
        punit = histalp_meta["unit"]
        print(param, "in", statn, ",", month, year, ":",
              histalp_data[year][month], punit)


# ----------------------------------------------------------------------
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.