Allow None for bits_per_values when saving GRIB data

earthkit/data/core/fieldlist.py

@@ -1177,6 +1177,13 @@ def save(self, filename, append=False, **kwargs):
             the target file be overwritten if already exists. Default is False
         **kwargs: dict, optional
             Other keyword arguments passed to :obj:`write`.
+
+        See Also
+        --------
+        :obj:`write`
+        :meth:`GribFieldList.save() <data.readers.grib.index.GribFieldList.save>`
+        :meth:`NumpyFieldList.save() <data.sources.numpy_list.NumpyFieldList.save>`
+
         """
         flag = "wb" if not append else "ab"
         with open(filename, flag) as f:
@@ -1191,6 +1198,11 @@ def write(self, f, **kwargs):
             The target file object.
         **kwargs: dict, optional
             Other keyword arguments passed to the underlying field implementation.
+
+        See Also
+        --------
+        read
+
         """
         for s in self:
             s.write(f, **kwargs)

earthkit/data/core/metadata.py

@@ -33,13 +33,23 @@ class Metadata(metaclass=ABCMeta):
     INDEX_KEYS = []
     CUSTOM_KEYS = [DATETIME]
 
+    extra = None
+
     def __iter__(self):
         """Return an iterator over the metadata keys."""
         return iter(self.keys())
 
-    @abstractmethod
     def __len__(self):
         r"""Return the number of metadata entries."""
+        if not self.extra:
+            return self._len()
+        else:
+            extra = sum([1 for x in self.extra if not self._contains(x)])
+            return extra + self._len()
+
+    @abstractmethod
+    def _len(self):
+        r"""Return the number of metadata entries without the extra items."""
         pass
 
     def __getitem__(self, key):
@@ -52,17 +62,30 @@ def __getitem__(self, key):
         """
         return self.get(key, raise_on_missing=True)
 
-    @abstractmethod
     def __contains__(self, key):
         r"""Check if ``key`` is available.
 
         Returns
         -------
         bool
         """
-        pass
+        if not self.extra:
+            return self._contains(key)
+        else:
+            if key in self.extra:
+                return True
+            return self._contains(key)
 
     @abstractmethod
+    def _contains(self, key):
+        r"""Check if ``key`` is available in the non extra-keys.
+
+        Returns
+        -------
+        bool
+        """
+        pass
+
     def keys(self):
         r"""Return the metadata keys.
 
@@ -71,16 +94,50 @@ def keys(self):
         Iterable of str
 
         """
-        pass
+        if not self.extra:
+            return self._keys()
+        else:
+            extra = [x for x in self.extra if x not in self._keys()]
+            if len(extra) == 0:
+                return self._keys()
+            else:
+                r = list(self._keys()) + extra
+                return r
 
     @abstractmethod
+    def _keys(self):
+        r"""Return the metadata keys without the extra keys.
+
+        Returns
+        -------
+        Iterable of str
+
+        """
+        pass
+
     def items(self):
         r"""Return the metadata items.
 
         Returns
         -------
         Iterable of :obj:`(key,value)` pairs
 
+        """
+        if not self.extra:
+            return self._items()
+        else:
+            r = dict(self._items())
+            r.update(self.extra)
+            return r.items()
+
+    @abstractmethod
+    def _items(self):
+        r"""Return the metadata items without the extra keys.
+
+        Returns
+        -------
+        Iterable of :obj:`(key,value)` pairs
+
         """
         pass
 
@@ -115,6 +172,8 @@ def get(self, key, default=None, *, astype=None, raise_on_missing=False):
             a missing value.
 
         """
+        if self._is_extra_key(key):
+            return self._get_extra_key(key, default=default, astype=astype)
         if self._is_custom_key(key):
             return self._get_custom_key(
                 key, default=default, astype=astype, raise_on_missing=raise_on_missing
@@ -128,6 +187,19 @@ def get(self, key, default=None, *, astype=None, raise_on_missing=False):
     def _get(self, key, astype=None, default=None, raise_on_missing=False):
         pass
 
+    def _is_extra_key(self, key):
+        return self.extra is not None and key in self.extra
+
+    def _get_extra_key(self, key, default=None, astype=None, **kwargs):
+        v = self.extra.get(key, default)
+
+        if astype is not None and v is not None:
+            try:
+                return astype(v)
+            except Exception:
+                return None
+        return v
+
     def _is_custom_key(self, key):
         return key in self.CUSTOM_KEYS and key not in self
 
@@ -300,9 +372,15 @@ def override(self, *args, **kwargs):
     def __len__(self):
         return len(self._d)
 
+    def _len(self):
+        return self._len()
+
     def __contains__(self, key):
         return key in self._d
 
+    def _contains(self, key):
+        pass
+
     def _get(self, key, astype=None, default=None, raise_on_missing=False):
         if not raise_on_missing:
             v = self._d.get(key, default)
@@ -319,9 +397,15 @@ def _get(self, key, astype=None, default=None, raise_on_missing=False):
     def keys(self):
         return self._d.keys()
 
+    def _keys(self):
+        pass
+
     def items(self):
         return self._d.items()
 
+    def _items(self):
+        pass
+
     def _base_datetime(self):
         return None
 

earthkit/data/readers/grib/codes.py

@@ -291,16 +291,25 @@ def __repr__(self):
     #         name = "paramId"
     #     return self.handle.get(name)
 
-    def write(self, f):
+    def write(self, f, bits_per_value=None):
         r"""Writes the message to a file object.
 
         Parameters
         ----------
         f: file object
             The target file object.
+        bits_per_value: int or None
+            Set the ``bitsPerValue`` GRIB key in the generated GRIB message. When
+            None the ``bitsPerValue`` stored in the metadata will be used.
         """
+        if bits_per_value is not None:
+            handle = self.handle.clone()
+            handle.set_long("bitsPerValue", bits_per_value)
+        else:
+            handle = self.handle
+
         # assert isinstance(f, io.IOBase)
-        self.handle.write_to(f)
+        handle.write_to(f)
 
     def message(self):
         r"""Returns a buffer containing the encoded message.

earthkit/data/readers/grib/index/__init__.py

@@ -14,7 +14,7 @@
 
 from earthkit.data.core.fieldlist import FieldList
 from earthkit.data.core.index import Index, MaskIndex, MultiIndex
-from earthkit.data.decorators import alias_argument
+from earthkit.data.decorators import alias_argument, detect_out_filename
 from earthkit.data.indexing.database import (
     FILEPARTS_KEY_NAMES,
     MORE_KEY_NAMES,
@@ -179,6 +179,33 @@ def _is_full_hypercube(self):
     def _normalize_kwargs_names(self, **kwargs):
         return kwargs
 
+    @detect_out_filename
+    def save(self, filename, append=False, bits_per_value=None):
+        r"""Write all the fields into a file.
+
+        Parameters
+        ----------
+        filename: str
+            The target file path.
+        append: bool
+            When it is true append data to the target file. Otherwise
+            the target file be overwritten if already exists.
+        bits_per_value: int or None
+            Set the ``bitsPerValue`` GRIB key for each message in the generated
+            output. When None the ``bitsPerValue`` stored in the message metadata
+            will be used.
+
+        See Also
+        --------
+        write
+
+        """
+        super().save(
+            filename,
+            append=append,
+            bits_per_value=bits_per_value,
+        )
+
 
 class GribMaskFieldList(GribFieldList, MaskIndex):
     def __init__(self, *args, **kwargs):