# Xarray to netcdf (ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all())

**URL:** <https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785>\
**Category:** Uncategorized\
**Created:** [January 1, 2025, 5:44pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785 "2025-01-01T17:44:08Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Toqeer](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@Toqeer](https://discourse.pangeo.io/u/Toqeer)\
**Post date:** [January 1, 2025, 5:44pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/1 "2025-01-01T17:44:08Z")

</div>

Dear All,

Using geemap and google colab I successfully exported ERA5\_L data to Netcdf format.  
I used the exported Netcdf data for further ingestion like seasonal mean etc , it works great.  
When I tried to save the data as netcdf , I got the following error :

**Xarray to netcdf (ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all())**

Even when I tried to export the original data to netcdf, it gives the same error.  
I checked the encoding, Fillvalue etc , everything is fine. But still i am getting the same error.

Here are the code snapshots:

```python
import xarray as xr
#Reading Data
fn="ISB_ERA5.nc"
ISB=xr.open_dataset(fn,engine="netcdf4")

```

```auto
<xarray.Dataset>
Dimensions: (time: 24, lon: 56, lat: 31)
Coordinates:
  * time (time) datetime64[ns] 2010-01-01 ... 2011-12-01
  * lon (lon) float64 72.78 72.79 72.8 ... 73.32 73.33
  * lat (lat) float64 33.5 33.51 33.52 ... 33.78 33.79 33.8
Data variables:
    total_precipitation_sum (time, lon, lat) float32 ...
Attributes:
    crs: EPSG:4326

```

```auto

```

Checking the encoding

```python
ISB.total_precipitation_sum.encoding

```

```auto
{'zlib': False,
 'szip': False,
 'zstd': False,
 'bzip2': False,
 'blosc': False,
 'shuffle': False,
 'complevel': 0,
 'fletcher32': False,
 'contiguous': True,
 'chunksizes': None,
 'source': '/Users/macbookpro/Documents/0_PM10_PM25/DATA_Scripts/ERA5L_DATA/ISB_ERA5.nc',
 'original_shape': (24, 56, 31),
 'dtype': dtype('float32'),
 '_FillValue': nan,
 'scale_factor': 0.01}

```

selecting by indexing and saving to _.nc_ formate file

```python
import netCDF4
single_timestep_data = ISB.isel(time=0)
ISB.to_netcdf("single_timestep_data.nc", mode='w', format='NETCDF4', engine='netcdf4')

```

 ![3](https://canada1.discourse-cdn.com/flex030/uploads/pangeo/original/2X/8/8538bb41325ab661797914005cae25bf8f8cac89.png)

Your suggestion/response to resolve this issue would be greatly appreciated.

Kind Regards  
Toqeer

---

<div class="post-metadata">

**Author:** ![rlourenco](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pangeo.io/rlourenco/32/2667_2.png) [@rlourenco](https://discourse.pangeo.io/u/rlourenco)\
**Post date:** [January 3, 2025, 11:46am UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/2 "2025-01-03T11:46:27Z")

</div>

Hi @Toqeer ! Does this still happen even if you persist/compute the computation before exporting? The subsetting can be affecting this, and triggering the computation upfront may help on debugging.

---

<div class="post-metadata">

**Author:** ![dcherian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pangeo.io/dcherian/32/2235_2.png) [@dcherian](https://discourse.pangeo.io/u/dcherian)\
**Post date:** [January 3, 2025, 2:35pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/3 "2025-01-03T14:35:27Z")

</div>

Can you share the full traceback please?

---

<div class="post-metadata">

**Author:** ![Toqeer](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@Toqeer](https://discourse.pangeo.io/u/Toqeer)\
**Post date:** [January 3, 2025, 3:55pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/4 "2025-01-03T15:55:56Z")

</div>

Dear @rlourenco thank you very much for the response. I face this problem after export.  
In google colab it works fine,  
Regards

---

<div class="post-metadata">

**Author:** ![Toqeer](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@Toqeer](https://discourse.pangeo.io/u/Toqeer)\
**Post date:** [January 3, 2025, 3:58pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/5 "2025-01-03T15:58:23Z")

</div>

Dear @dcherian thanks for the quick response, here is the traceback error

```python
import netCDF4
single_timestep_data = ISB.isel(time=0)
ISB.to_netcdf("single_timestep_data.nc", mode='w', format='NETCDF4', engine='netcdf4')

```

```auto
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Cell In[170], line 3
      1 import netCDF4
      2 single_timestep_data = ISB.isel(time=0)
----> 3 ISB.to_netcdf("single_timestep_data.nc", mode='w', format='NETCDF4', engine='netcdf4')

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/core/dataset.py:2041, in Dataset.to_netcdf(self, path, mode, format, group, engine, encoding, unlimited_dims, compute, invalid_netcdf)
   2038 encoding = {}
   2039 from xarray.backends.api import to_netcdf
-> 2041 return to_netcdf( # type: ignore # mypy cannot resolve the overloads:(
   2042 self,
   2043 path,
   2044 mode=mode,
   2045 format=format,
   2046 group=group,
   2047 engine=engine,
   2048 encoding=encoding,
   2049 unlimited_dims=unlimited_dims,
   2050 compute=compute,
   2051 multifile=False,
   2052 invalid_netcdf=invalid_netcdf,
   2053 )

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/api.py:1246, in to_netcdf(dataset, path_or_file, mode, format, group, engine, encoding, unlimited_dims, compute, multifile, invalid_netcdf)
   1241 # TODO: figure out how to refactor this logic (here and in save_mfdataset)
   1242 # to avoid this mess of conditionals
   1243 try:
   1244 # TODO: allow this work (setting up the file for writing array data)
   1245 # to be parallelized with dask
-> 1246 dump_to_store(
   1247 dataset, store, writer, encoding=encoding, unlimited_dims=unlimited_dims
   1248 )
   1249 if autoclose:
   1250 store.close()

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/api.py:1293, in dump_to_store(dataset, store, writer, encoder, encoding, unlimited_dims)
   1290 if encoder:
   1291 variables, attrs = encoder(variables, attrs)
-> 1293 store.store(variables, attrs, check_encoding, writer, unlimited_dims=unlimited_dims)

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/common.py:352, in AbstractWritableDataStore.store(self, variables, attributes, check_encoding_set, writer, unlimited_dims)
    349 if writer is None:
    350 writer = ArrayWriter()
--> 352 variables, attributes = self.encode(variables, attributes)
    354 self.set_attributes(attributes)
    355 self.set_dimensions(variables, unlimited_dims=unlimited_dims)

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/common.py:441, in WritableCFDataStore.encode(self, variables, attributes)
    438 def encode(self, variables, attributes):
    439 # All NetCDF files get CF encoded by default, without this attempting
    440 # to write times, for example, would fail.
--> 441 variables, attributes = cf_encoder(variables, attributes)
    442 variables = {k: self.encode_variable(v) for k, v in variables.items()}
    443 attributes = {k: self.encode_attribute(v) for k, v in attributes.items()}

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/conventions.py:784, in cf_encoder(variables, attributes)
    782 for var in new_vars.values():
    783 bounds = var.attrs["bounds"] if "bounds" in var.attrs else None
--> 784 if bounds and bounds in new_vars:
    785 # see http://cfconventions.org/cf-conventions/cf-conventions.html#cell-boundaries
    786 for attr in [
    787 "units",
    788 "standard_name",
   (...)
    795 "month_lengths",
    796 ]:
    797 if attr in new_vars[bounds].attrs and attr in var.attrs:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

```

---

<div class="post-metadata">

**Author:** ![dcherian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pangeo.io/dcherian/32/2235_2.png) [@dcherian](https://discourse.pangeo.io/u/dcherian)\
**Post date:** [January 3, 2025, 6:11pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/6 "2025-01-03T18:11:20Z")

</div>

Thanks the `bounds` attribute is an ndarray and `if bounds` is failing.Can you open an issue at [GitHub - pydata/xarray: N-D labeled arrays and datasets in Python](https://github.com/pydata/xarray) please? As a temporary fix, you can set `x.attrs["bounds"] = list(x.attrs["bounds"]` where x is a DataArray

---

<div class="post-metadata">

**Author:** ![Toqeer](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@Toqeer](https://discourse.pangeo.io/u/Toqeer)\
**Post date:** [January 4, 2025, 2:58pm UTC](https://discourse.pangeo.io/t/xarray-to-netcdf-valueerror-the-truth-value-of-an-array-with-more-than-one-element-is-ambiguous-use-a-any-or-a-all/4785/7 "2025-01-04T14:58:01Z")

</div>

Dear @dcherian. Thank you very much for the suggestion, the problem is solved. Just a little correction, instead of `list`, `tuple` works i.e  
`x.attrs["bounds"] = tuple(x.attrs["bounds"])` , where x is a DataArray.

The use of `list `, `x.attrs["bounds"] = list(x.attrs["bounds"])`  
results in the following error

```auto
TypeError: unhashable type: 'list'
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
Cell In[189], line 2
      1 import netCDF4
----> 2 ISB.to_netcdf('ISBm.nc',format='NETCDF4', engine='netcdf4')

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/core/dataset.py:2041, in Dataset.to_netcdf(self, path, mode, format, group, engine, encoding, unlimited_dims, compute, invalid_netcdf)
   2038 encoding = {}
   2039 from xarray.backends.api import to_netcdf
-> 2041 return to_netcdf( # type: ignore # mypy cannot resolve the overloads:(
   2042 self,
   2043 path,
   2044 mode=mode,
   2045 format=format,
   2046 group=group,
   2047 engine=engine,
   2048 encoding=encoding,
   2049 unlimited_dims=unlimited_dims,
   2050 compute=compute,
   2051 multifile=False,
   2052 invalid_netcdf=invalid_netcdf,
   2053 )

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/api.py:1246, in to_netcdf(dataset, path_or_file, mode, format, group, engine, encoding, unlimited_dims, compute, multifile, invalid_netcdf)
   1241 # TODO: figure out how to refactor this logic (here and in save_mfdataset)
   1242 # to avoid this mess of conditionals
   1243 try:
   1244 # TODO: allow this work (setting up the file for writing array data)
   1245 # to be parallelized with dask
-> 1246 dump_to_store(
   1247 dataset, store, writer, encoding=encoding, unlimited_dims=unlimited_dims
   1248 )
   1249 if autoclose:
   1250 store.close()

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/api.py:1293, in dump_to_store(dataset, store, writer, encoder, encoding, unlimited_dims)
   1290 if encoder:
   1291 variables, attrs = encoder(variables, attrs)
-> 1293 store.store(variables, attrs, check_encoding, writer, unlimited_dims=unlimited_dims)

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/common.py:352, in AbstractWritableDataStore.store(self, variables, attributes, check_encoding_set, writer, unlimited_dims)
    349 if writer is None:
    350 writer = ArrayWriter()
--> 352 variables, attributes = self.encode(variables, attributes)
    354 self.set_attributes(attributes)
    355 self.set_dimensions(variables, unlimited_dims=unlimited_dims)

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/backends/common.py:441, in WritableCFDataStore.encode(self, variables, attributes)
    438 def encode(self, variables, attributes):
    439 # All NetCDF files get CF encoded by default, without this attempting
    440 # to write times, for example, would fail.
--> 441 variables, attributes = cf_encoder(variables, attributes)
    442 variables = {k: self.encode_variable(v) for k, v in variables.items()}
    443 attributes = {k: self.encode_attribute(v) for k, v in attributes.items()}

File ~/Codes/anaconda3/envs/geosp/lib/python3.9/site-packages/xarray/conventions.py:784, in cf_encoder(variables, attributes)
    782 for var in new_vars.values():
    783 bounds = var.attrs["bounds"] if "bounds" in var.attrs else None
--> 784 if bounds and bounds in new_vars:
    785 # see http://cfconventions.org/cf-conventions/cf-conventions.html#cell-boundaries
    786 for attr in [
    787 "units",
    788 "standard_name",
   (...)
    795 "month_lengths",
    796 ]:
    797 if attr in new_vars[bounds].attrs and attr in var.attrs:

TypeError: unhashable type: 'list'

```

Thank you very much