Fix linting errors (#1226)

* Fix variable possible unbound error

* Avoid extra version check

This avoids having to check the version twice: once in the "in [2,3]" and
also in the if/elif statement. It also fixes linting error of normalize_store
being possibly unbound.

* Add Optional where necessary to indicate that value could be None

Author: caviere

zarr/creation.py

@@ -1,3 +1,4 @@
+from typing import Optional
 from warnings import warn
 
 import numpy as np
@@ -17,7 +18,7 @@
 
 
 def create(shape, chunks=True, dtype=None, compressor='default',
-           fill_value=0, order='C', store=None, synchronizer=None,
+           fill_value: Optional[int] = 0, order='C', store=None, synchronizer=None,
            overwrite=False, path=None, chunk_store=None, filters=None,
            cache_metadata=True, cache_attrs=True, read_only=False,
            object_codec=None, dimension_separator=None, write_empty_chunks=True,

zarr/hierarchy.py

@@ -157,6 +157,7 @@ def __init__(self, store, path=None, read_only=False, chunk_store=None,
             raise ContainsArrayError(path)
 
         # initialize metadata
+        mkey = None
         try:
             mkey = _prefix_to_group_key(self._store, self._key_prefix)
             assert not mkey.endswith("root/.group")
@@ -1277,6 +1278,7 @@ def group(store=None, overwrite=False, chunk_store=None,
 
     path = normalize_storage_path(path)
 
+    requires_init = None
     if zarr_version == 2:
         requires_init = overwrite or not contains_group(store)
     elif zarr_version == 3:

zarr/storage.py

@@ -161,13 +161,13 @@ def normalize_store_arg(store: Any, storage_options=None, mode="r", *,
     if zarr_version is None:
         # default to v2 store for backward compatibility
         zarr_version = getattr(store, "_store_version", DEFAULT_ZARR_VERSION)
-    elif zarr_version not in [2, 3]:
-        raise ValueError("zarr_version must be either 2 or 3")
     if zarr_version == 2:
         normalize_store = _normalize_store_arg_v2
     elif zarr_version == 3:
         from zarr._storage.v3 import _normalize_store_arg_v3
         normalize_store = _normalize_store_arg_v3
+    else:
+        raise ValueError("zarr_version must be either 2 or 3")
     return normalize_store(store, storage_options, mode)
 
 
@@ -597,7 +597,7 @@ def init_group(
     store: StoreLike,
     overwrite: bool = False,
     path: Path = None,
-    chunk_store: StoreLike = None,
+    chunk_store: Optional[StoreLike] = None,
 ):
     """Initialize a group store. Note that this is a low-level function and there should be no
     need to call this directly from user code.
@@ -644,7 +644,7 @@ def _init_group_metadata(
     store: StoreLike,
     overwrite: Optional[bool] = False,
     path: Optional[str] = None,
-    chunk_store: StoreLike = None,
+    chunk_store: Optional[StoreLike] = None,
 ):
 
     store_version = getattr(store, '_store_version', 2)