autonotebook: check for ipywidgets

- closes #1218
- fixes #1082
- fixes #1217

tqdm/autonotebook.py

@@ -8,6 +8,7 @@ Usage:
 """
 import os
 import sys
+from warnings import warn
 
 try:
     get_ipython = sys.modules['IPython'].get_ipython
@@ -15,11 +16,14 @@ try:
         raise ImportError("console")
     if 'VSCODE_PID' in os.environ:  # pragma: no cover
         raise ImportError("vscode")
+    from .notebook import WARN_NOIPYW, IProgress
+    if IProgress is None:
+        from .std import TqdmWarning
+        warn(WARN_NOIPYW, TqdmWarning, stacklevel=2)
+        raise ImportError('ipywidgets')
 except Exception:
     from .std import tqdm, trange
 else:  # pragma: no cover
-    from warnings import warn
-
     from .notebook import tqdm, trange
     from .std import TqdmExperimentalWarning
     warn("Using `tqdm.autonotebook.tqdm` in notebook mode."

tqdm/notebook.py

@@ -71,6 +71,9 @@ if True:  # pragma: no cover
 
 __author__ = {"github.com/": ["lrq3000", "casperdcl", "alexanderkuk"]}
 __all__ = ['tqdm_notebook', 'tnrange', 'tqdm', 'trange']
+WARN_NOIPYW = ("IProgress not found. Please update jupyter and ipywidgets."
+               " See https://ipywidgets.readthedocs.io/en/stable"
+               "/user_install.html")
 
 
 class TqdmHBox(HBox):
@@ -112,10 +115,7 @@ class tqdm_notebook(std_tqdm):
 
         # Prepare IPython progress bar
         if IProgress is None:  # #187 #451 #558 #872
-            raise ImportError(
-                "IProgress not found. Please update jupyter and ipywidgets."
-                " See https://ipywidgets.readthedocs.io/en/stable"
-                "/user_install.html")
+            raise ImportError(WARN_NOIPYW)
         if total:
             pbar = IProgress(min=0, max=total)
         else:  # No total? Show info style bar with no progress tqdm status