# -*- coding: utf-8 -*-
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"""Module for generating IMPROVER-compliant file names."""
from iris.exceptions import CoordinateNotFoundError
[docs]def generate_file_name(cube, parameter=None, include_period=False):
"""
From a forecast cube, generate an IMPROVER-suitable file name using the
correct lead time. Based on existing StaGE functionality. Requires a
"time" coordinate. If the cube has no "forecast_period" coordinate (for
example if the input is a radar composite or other observation), this
function creates a dummy string representing a forecast period of zero.
The filename generated will be of the format:
20180806T2300Z-PT0012H00M-lwe_precip_rate.nc.
If a period is included, the filename will become:
20180806T2300Z-PT0012H00M-lwe_precip_accumulation-PT03H.nc
Args:
cube (iris.cube.Cube):
Cube containing nowcast data
parameter (str):
Optional parameter name to use in the output filename rather than
taking the name of the cube diagnostic.
include_period (bool):
Optional argument to indicate whether a period, accumulation or
time window identifier should be included within the filename.
Returns:
str:
File base name to which to write
Raises:
ValueError: In order to calculate the period, either the
forecast_period or the time coordinate must have bounds.
ValueError: The period deduced by the coordinate bounds must be either
less than 1 hour or in terms of whole hours.
"""
vtime = (cube.coord('time').units).num2date(cube.coord('time').points)[0]
validity_time_string = '{:04}{:02}{:02}T{:02}{:02}Z'.format(
vtime.year, vtime.month, vtime.day, vtime.hour, vtime.minute)
try:
forecast_period_coord = cube.coord('forecast_period').copy()
forecast_period_coord.convert_units('s')
forecast_period, = forecast_period_coord.points
forecast_period_hours = int(forecast_period // 3600)
forecast_period_minutes = int(
(forecast_period - 3600*forecast_period_hours)) // 60
forecast_period_string = 'PT{:04}H{:02}M'.format(
forecast_period_hours, forecast_period_minutes)
except CoordinateNotFoundError:
forecast_period_string = 'PT0000H00M'
if parameter is None:
parameter = cube.name().replace(' ', '_').lower()
for char in ["/", "(", ")"]:
parameter = parameter.replace(char, '')
parameter = parameter.replace('__', '_')
period_string = None
if include_period:
# If a period should be included within the filename, then check the
# forecast_period and time coordinates for bounds that can be used
# to define the period. Depending upon the bounds specified by the
# coordinates, the format of the period will either be 'PT??M'
# to represent a period in minutes, where ?? will be replaced by the
# actual minutes, or 'PT??H' to represent a period in hours, where ??
# will be replaced by the actual hours.
coord_units = {"forecast_period": "seconds",
"time": "seconds since 1970-01-01 00:00:00"}
for coord_name in ["forecast_period", "time"]:
if cube.coords(coord_name):
coord = cube.coord(coord_name).copy()
if hasattr(coord, "bounds") and coord.bounds is not None:
coord.convert_units(coord_units[coord_name])
break
else:
msg = ("Neither the forecast_period coordinate nor the time "
"coordinate has bounds. Therefore the period required "
"for the filename could not be calculated.")
raise ValueError(msg)
bounds_diff = coord.bounds[0][1] - coord.bounds[0][0]
bounds_diff_hours = int(bounds_diff // 3600)
bounds_diff_minutes = int(
(bounds_diff - 3600*bounds_diff_hours)) // 60
if bounds_diff_minutes:
if bounds_diff_hours:
msg = ("If the difference between the bounds of the {} "
"coordinate should either be less than one hour "
"or should in terms of whole hours."
"Differences in the hours of {} and in the minutes "
"of {} is not supported.".format(
coord_name, bounds_diff_hours,
bounds_diff_minutes))
raise ValueError(msg)
period_string = 'PT{:02}M'.format(forecast_period_minutes)
else:
period_string = 'PT{:02}H'.format(forecast_period_hours)
# Construct filename with or without an additional string to describe the
# accumulation period or time window of relevance.
if include_period:
filename = '{}-{}-{}-{}.nc'.format(
validity_time_string, forecast_period_string, parameter,
period_string)
else:
filename = '{}-{}-{}.nc'.format(
validity_time_string, forecast_period_string, parameter)
return filename