Downloading the daily mean of ERA5.

parm_name='uwind'

year=2010

month=01

c = cdsapi.Client()
c.retrieve('reanalysis-era5-pressure-levels',

{ 'product_type':'reanalysis',

'variable':parm_name,

'year':year,

'month':month,

'pressure_level':['1000', '975', '950', '925', '900', '875', '850', '825', '800', '775', '750', '700', '650', '600', '550', '500', '450', '400', '350', '300', '250', '225', '200', '175', '150', '125', '100', '70', '50', '30', '20' , '10' , '7' , '5' , '3', '2' , '1'],

'day':['01','02','03','04','05', '06','07','08','09','10', '11','12','13','14','15', '16','17','18','19','20', '21','22','23','24','25', '26','27','28','29','30','31'],

'time':[ '00:00','01:00','02:00', '03:00','04:00','05:00', '06:00','07:00','08:00', '09:00','10:00','11:00', '12:00','13:00','14:00', '15:00','16:00','17:00', '18:00','19:00','20:00', '21:00','22:00','23:00'],

'format':'netcdf', 'grid': [1,1], # latitude and longitude grid: east-west and north-south.

'area': [50,-180,-50,180] # north, west, south, and east }

,diri_input+"%s_%s_%s.nc"%(parm_name,year,month))