Python3.6 idioms (#3419)

* pyupgrade --py36-plus

* Update xarray/core/nputils.py

Co-Authored-By: crusaderky <[email protected]>

* Update xarray/core/parallel.py

Co-Authored-By: crusaderky <[email protected]>

* Update xarray/tests/test_cftime_offsets.py

Co-Authored-By: crusaderky <[email protected]>

* Update xarray/tests/test_cftime_offsets.py

Co-Authored-By: crusaderky <[email protected]>

Author: max-sixty

doc/gallery/plot_cartopy_facetgrid.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
 ==================================
 Multiple plots and map projections

doc/gallery/plot_colorbar_center.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
 ==================
 Centered colormaps

doc/gallery/plot_control_colorbar.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
 ===========================
 Control the plot's colorbar

doc/gallery/plot_lines_from_2d.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
 ==================================
 Multiple lines from a 2d DataArray

doc/gallery/plot_rasterio.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
 .. _recipes.rasterio:
 

doc/gallery/plot_rasterio_rgb.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
 .. _recipes.rasterio_rgb:
 

xarray/_version.py

@@ -94,7 +94,7 @@ def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False, env=
             return None, None
     else:
         if verbose:
-            print("unable to find command, tried %s" % (commands,))
+            print(f"unable to find command, tried {commands}")
         return None, None
     stdout = p.communicate()[0].strip()
     if sys.version_info[0] >= 3:
@@ -302,9 +302,8 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
             if verbose:
                 fmt = "tag '%s' doesn't start with prefix '%s'"
                 print(fmt % (full_tag, tag_prefix))
-            pieces["error"] = "tag '%s' doesn't start with prefix '%s'" % (
-                full_tag,
-                tag_prefix,
+            pieces["error"] = "tag '{}' doesn't start with prefix '{}'".format(
+                full_tag, tag_prefix
             )
             return pieces
         pieces["closest-tag"] = full_tag[len(tag_prefix) :]

xarray/backends/api.py

@@ -718,7 +718,7 @@ def open_mfdataset(
     autoclose=None,
     parallel=False,
     join="outer",
-    **kwargs
+    **kwargs,
 ):
     """Open multiple files as a single dataset.
 
@@ -1258,9 +1258,7 @@ def _validate_append_dim_and_encoding(
         return
     if append_dim:
         if append_dim not in ds.dims:
-            raise ValueError(
-                "{} not a valid dimension in the Dataset".format(append_dim)
-            )
+            raise ValueError(f"{append_dim} not a valid dimension in the Dataset")
     for data_var in ds_to_append:
         if data_var in ds:
             if append_dim is None:

xarray/backends/file_manager.py

@@ -83,7 +83,7 @@ def __init__(
         kwargs=None,
         lock=None,
         cache=None,
-        ref_counts=None
+        ref_counts=None,
     ):
         """Initialize a FileManager.
 
@@ -267,7 +267,7 @@ def __setstate__(self, state):
     def __repr__(self):
         args_string = ", ".join(map(repr, self._args))
         if self._mode is not _DEFAULT_MODE:
-            args_string += ", mode={!r}".format(self._mode)
+            args_string += f", mode={self._mode!r}"
         return "{}({!r}, {}, kwargs={})".format(
             type(self).__name__, self._opener, args_string, self._kwargs
         )

xarray/backends/netCDF4_.py

@@ -137,7 +137,7 @@ def _nc4_dtype(var):
     elif var.dtype.kind in ["i", "u", "f", "c", "S"]:
         dtype = var.dtype
     else:
-        raise ValueError("unsupported dtype for netCDF4 variable: {}".format(var.dtype))
+        raise ValueError(f"unsupported dtype for netCDF4 variable: {var.dtype}")
     return dtype