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I have 28 files for example :-

File -> day01.nc inside file:-

| lat | lon | date      |
| --- | --- | --------  |
| 7   | 68  | 2021-02-01|
| 7   | 69  | 2021-02-01|

File -> day02.nc inside file:-

| lat | lon | date      |
| --- | --- | --------  |
| 7   | 68  | 2021-02-02|
| 7   | 69  | 2021-02-02|

File -> day28.nc inside file:-

| lat | lon | date      |
| --- | --- | --------  |
| 7   | 68  | 2021-02-28|
| 7   | 69  | 2021-02-28|

I want to convert their name according to date format like temp_ind20210201.nc, temp_ind20210202.nc,...,temp_ind20210328.nc using python script.

Note :- In day01.nc the date format inside that file is like 2021-02-01 and so on. I was trying :-

DATA_DIR = 'data'
today = datetime.datetime.now()
offset_1day = datetime.timedelta(days=1)
re_number = re.compile('day(\d{,2})\.nc')

for fname in glob.glob(DATA_DIR + "/*.nc"):
      number_string = re_number.search(fname)
if not number_string:
      continue
   number_of_days = int(number_string.group(1))
   str_timestamp = (today + (number_of_days - 1) * offset_1day).strftime("%Y%m%d")
   new_fname = f"{DATA_DIR}/temp_ind{_str_timestamp}.nc"
   print(f'{fname} -> {new_fname}')
   os.rename(fname, new_fname)
tech Tuple
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  • how are u deciding the `month`? – Epsi95 Feb 24 '21 at 08:31
  • actually this is current month data starts from date 17-02-2021 to end with 18-03-2021. – tech Tuple Feb 24 '21 at 08:43
  • you also could have edited your [other question](https://stackoverflow.com/q/66345679/10197418), it can be re-opened. Anyways, regarding your question as it is now, so you basically want to read the nc file, extract the first entry from "date", close the file and rename it according to what you have extracted? – FObersteiner Feb 24 '21 at 08:53
  • yes that is what I want using python script. I am not able to get the date from inside the file and set it into the file name. Please help. – tech Tuple Feb 24 '21 at 09:01
  • did you have a look at [netCDF4](https://unidata.github.io/netcdf4-python/)? there's also some questions related to reading nc files in Python here on SO. for your specific case, it is kind of difficult to give a good answer without an example .nc file (there could be groups, date could be in different formats etc.). – FObersteiner Feb 24 '21 at 09:09

2 Answers2

1

Based on the question and comments beneath it, you want to be able to extract the first date in a NetCDF file and use that to generate a new file name for that file. The following should work, but might need tweaking, depending on how time is formatted:

import xarray as xr
ds = xr.open_dataset("infile.nc")
"temp_ind" + ds.time[0].values.astype("str")[0:10].replace("-","") + ".nc"
Robert Wilson
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0

I would probably do this in a loop from the command line in bash. I pipe the output from CDO to awk, in case any file has more than one date, this will ensure that the file is renamed to the first date in the file

for file in day*.nc ; do 
   mv $file temp_ind`cdo -s showdate $file | awk '{print $1}'`.nc
done

note that CDO outputs a date with hyphens yyyy-mm-dd, so you get a filename with hyphens included - you can remove those with a second pipe to sed if you don't like that.

ClimateUnboxed
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