Infer type from default if provided but type omitted

README.rst

@@ -38,14 +38,24 @@ Get them:
     'true'
     >>> getenv('BOOLEAN', type=bool)
     True
+    >>> getenv('BOOLEAN', default=False)
+    True
     >>> getenv('LIST', type=list)
     ['a', 'b', 'c']
+    >>> getenv('LIST', default=[1, 2, 3])
+    ['a', 'b', 'c']
     >>> getenv('LIST', type=tuple)
     ('a', 'b', 'c')
+    >>> getenv('LIST', default=(1, 2, 3))
+    ('a', 'b', 'c')
     >>> getenv('TRICKY_LIST', type=list, separator=':')
     ['d', 'e', 'f']
+    >>> getenv('TRICKY_LIST', default=[1, 2, 3], separator=':')
+    ['d', 'e', 'f']
     >>> getenv('DICT', type=dict)
     {'foo': 'bar'}
+    >>> getenv('DICT', default={'key': 'value'})
+    {'foo': 'bar'}
     >>> getenv('LOST', default='default value anyone?')
     'default value anyone?'
 

smart_getenv.py

@@ -1,18 +1,19 @@
 import os
 from ast import literal_eval
 
-
-__version__ = '1.1.0'
+__version__ = '1.2.0'
 
 
 def getenv(name, **kwargs):
     """
     Retrieves environment variable by name and casts the value to desired type.
     If desired type is list or tuple - uses separator to split the value.
     """
-    default_value = kwargs.pop('default', None)
-    desired_type = kwargs.pop('type', str)
-    list_separator = kwargs.pop('separator', ',')
+    default_value = kwargs.get('default', None)
+    list_separator = kwargs.get('separator', ',')
+    desired_type = kwargs.get('type')
+    if not desired_type and default_value is not None:
+        desired_type = type(default_value)
 
     value = os.getenv(name, None)
 
@@ -28,7 +29,7 @@ def getenv(name, **kwargs):
         else:
             return bool(value)
 
-    if desired_type is list or desired_type is tuple:
+    if desired_type in (list, tuple):
         value = value.split(list_separator)
         return desired_type(value)
 

tests.py

@@ -40,6 +40,7 @@ def test_getenv_type_str(self):
         """
         os.environ[self.test_var_name] = 'abc'
         self.assertEqual(getenv(self.test_var_name, type=str), 'abc')
+        self.assertEqual(getenv(self.test_var_name, default='qwe'), 'abc')
 
     def test_getenv_type_int(self):
         """
@@ -58,6 +59,9 @@ def test_getenv_type_int(self):
         except ValueError:
             pass
 
+        os.environ[self.test_var_name] = '2'
+        self.assertEqual(getenv(self.test_var_name, default=1), 2)
+
     def test_getenv_type_float(self):
         """
         If environment variable exists and desired type is float:
@@ -75,6 +79,9 @@ def test_getenv_type_float(self):
         except ValueError:
             pass
 
+        os.environ[self.test_var_name] = '123.4'
+        self.assertEqual(getenv(self.test_var_name, default=245.6), 123.4)
+
     def test_getenv_type_bool(self):
         """
         If environment variable exists and desired type is bool, ensure getenv returns bool.
@@ -106,6 +113,9 @@ def test_getenv_type_bool(self):
         os.environ[self.test_var_name] = ''
         self.assertEqual(getenv(self.test_var_name, type=bool), False)
 
+        os.environ[self.test_var_name] = 'absolutely not a boolean'
+        self.assertEqual(getenv(self.test_var_name, default=False), True)
+
     def test_getenv_type_list(self):
         """
         If environment variable exists and desired type is list:
@@ -125,6 +135,9 @@ def test_getenv_type_list(self):
         os.environ[self.test_var_name] = 'a:b:c'
         self.assertEqual(getenv(self.test_var_name, type=list, separator=':'), ['a', 'b', 'c'])
 
+        os.environ[self.test_var_name] = 'a,b,c'
+        self.assertEqual(getenv(self.test_var_name, default=[1, 2]), ['a', 'b', 'c'])
+
     def test_getenv_type_tuple(self):
         """
         If environment variable exists and desired type is tuple:
@@ -144,6 +157,9 @@ def test_getenv_type_tuple(self):
         os.environ[self.test_var_name] = 'a:b:c'
         self.assertEqual(getenv(self.test_var_name, type=tuple, separator=':'), ('a', 'b', 'c'))
 
+        os.environ[self.test_var_name] = 'a,b,c'
+        self.assertEqual(getenv(self.test_var_name, default=(1, 2)), ('a', 'b', 'c'))
+
     def test_getenv_type_dict(self):
         """
         If environment variable exists and desired type is dict:
@@ -169,6 +185,9 @@ def test_getenv_type_dict(self):
         except SyntaxError:
             pass
 
+        os.environ[self.test_var_name] = '{    "key":    "value"      }'
+        self.assertEqual(getenv(self.test_var_name, default={"key": "other value"}), {'key': 'value'})
+
 
 if __name__ == '__main__':
     unittest.main()