How to use XArray to merge specific netcdf4

Question

Background

I have 2 years worth of netcdf4 files (1 netcdf4 file per day). I have been using X-Array to merge files making them easy to use. All netcdf4 files follow same naming convention "YYYYMMDD_data_Nx.nc4.nc"

Question

However what do I do if I only want to use a subset of subset of my data, for example files between 1/1/2019 and 31/1/2019.

What I've currently got

import xarray as xr

ds = xr.open_dataset('C:\\Users\\FILES\\*.nc')
df = ds
df.to_csv('export.csv', index=True)

Answer 1

Solved

I've looked at the xarray readthedocs page, saw this blurb in the open_mfdataset page.

paths (str or sequence) – Either a string glob in the form "path/to/my/files/*.nc" or an explicit list of files to open. Paths can be given as strings or as pathlib Paths. If concatenation along more than one dimension is desired, then paths must be a nested list-of-lists (see manual_combine for details). (A string glob will be expanded to a 1-dimensional list.)

As such I passed through a list

Updated & Working Code

import xarray as xr
from datetime import timedelta, date, datetime
import pandas as pd
import numpy as np


# **************
# Date Ranges
# **************
def daterange(start_date, end_date):
    for n in range(int((end_date - start_date).days)):
        yield start_date + timedelta(n)


# Start & End Date
start_date = date(2019, 1, 1)
end_date = date(2019, 1, 31)

# Empty List
filepath = 'C:\\Users\\USER\\FILES\\'
filelist = []

# Loop through all MERRA2 files and add the ones we need to the list
for single_date in daterange(start_date, end_date):
    YYYY = single_date.strftime("%Y")
    MM = single_date.strftime("%m")
    DD = single_date.strftime("%d")
    filename = filepath + YYYY + MM + DD + '_data_Nx.nc'

    filelist.append(filename)

# Merge via X-Array and export to csv
ds = xr.open_mfdataset(filelist, combine='by_coords')
df = ds.to_dataframe()
df.to_csv('export.csv', index=True)