MAINT: Nicely inform users if they're missing hard dependencies.

closes #12176
closes #12468

Author: Marco Farrugia

pandas/__init__.py

@@ -4,8 +4,21 @@
 
 __docformat__ = 'restructuredtext'
 
+# Let users know if they're missing any of our hard dependencies
+hard_dependencies = ("numpy", "pytz", "dateutil")
+missing_dependencies = []
+
+for dependency in hard_dependencies:
+    try:
+        __import__(dependency)
+    except ImportError as e:
+        missing_dependencies.append(dependency)
+
+if missing_dependencies:
+    raise ImportError("Missing required dependencies {0}".format(missing_dependencies))
+
+
 # numpy compat
-import numpy as np
 from pandas.compat.numpy_compat import *
 
 try:
@@ -49,4 +62,3 @@
 v = get_versions()
 __version__ = v.get('closest-tag',v['version'])
 del get_versions, v
-

pandas/compat/numpy_compat.py

@@ -66,7 +66,8 @@ def np_array_datetime64_compat(arr, *args, **kwargs):
 
     return np.array(arr, *args, **kwargs)
 
-__all__ = ['_np_version',
+__all__ = ['np',
+           '_np_version',
            '_np_version_under1p8',
            '_np_version_under1p9',
            '_np_version_under1p10',