Added bidirectional dict function & appropriate tests

Author: domdfcoding

domdf_python_tools/utils.py

@@ -115,7 +115,7 @@ def list2string(the_list, sep=","):
 	Convert a list to a comma separated string
 
 	:param the_list: The list to convert to a string
-	:type the_list: list
+	:type the_list: list, tuple
 	:param sep: Separator to use for the string, default ","
 	:type sep: str
 
@@ -131,7 +131,7 @@ def list2str(the_list, sep=","):
 	Convert a list to a comma separated string
 	
 	:param the_list: The list to convert to a string
-	:type the_list: list
+	:type the_list: list, tuple
 	:param sep: Separator to use for the string, default ","
 	:type sep: str
 	
@@ -172,3 +172,52 @@ def permutations(data, n=2):
 		if i[::-1] not in perms:
 			perms.append(i)
 	return perms
+
+
+class bdict(dict):
+	"""
+	Returns a new dictionary initialized from an optional positional argument
+		and a possibly empty set of keyword arguments.
+	
+	Each key:value pair is entered into the dictionary in both directions,
+		so you can perform lookups with either the key or the value.
+	
+	If no positional argument is given, an empty dictionary is created.
+	If a positional argument is given and it is a mapping object, a dictionary
+		is created with the same key-value pairs as the mapping object.
+	Otherwise, the positional argument must be an iterable object.
+		Each item in the iterable must itself be an iterable with exactly two
+		objects. The first object of each item becomes a key in the new
+		dictionary, and the second object the corresponding value.
+	
+	If keyword arguments are given, the keyword arguments and their values are
+	added to the dictionary created from the positional argument.
+	
+	If an attempt is made to add a key or value that already exists in the
+		dictionary a ValueError will be raised
+	
+	Based on https://stackoverflow.com/a/1063393 by https://stackoverflow.com/users/9493/brian
+	"""
+	
+	def __init__(self, *args, **kwargs):
+		super().__init__(self)
+		if len(args) == 1:
+			for key, value in dict(*args).items():
+				self.__setitem__(key, value)
+		if len(args) == 0:
+			for key, value in kwargs.items():
+				self.__setitem__(key, value)
+
+	def __setitem__(self, key, val):
+		if key in self or val in self:
+			if key in self and self[key] != val:
+				raise ValueError(f"The key '{key}' is already present in the dictionary")
+			if val in self and self[val] != key:
+				raise ValueError(f"The key '{val}' is already present in the dictionary")
+				
+		dict.__setitem__(self, key, val)
+		dict.__setitem__(self, val, key)
+	
+	def __delitem__(self, key):
+		dict.__delitem__(self, self[key])
+		dict.__delitem__(self, key)

tests/test_init.py

@@ -13,60 +13,6 @@
 
 def test_pyversion():
 	assert isinstance(pyversion, int)
-
-def test_str2tuple():
-	assert isinstance(str2tuple("1,2,3"), tuple) # tests without spaces
-	assert isinstance(str2tuple("1, 2, 3"), tuple) # tests with spaces
-	assert isinstance(str2tuple("1; 2; 3", sep=";"), tuple) # tests with semicolon
-	if str2tuple("1,2,3") == (1, 2, 3):
-		assert 1
-	else:
-		assert 0
-		
-def test_tuple2str():
-	assert isinstance(tuple2str(("1","2","3",)), str)
-	if tuple2str((1, 2, 3)) == "1,2,3":
-		assert 1
-	else:
-		assert 0
-		
-	assert isinstance(tuple2str((1,2,3,), sep=";"), str) # tests with semicolon
-	if tuple2str((1, 2, 3), sep=";") == "1;2;3":
-		assert 1
-	else:
-		assert 0
-
-def test_chunks():
-	assert isinstance(chunks(list(range(100)), 5), types.GeneratorType)
-	if list(chunks(list(range(100)), 5))[0] == [0,1,2,3,4]:
-		assert 1
-	else:
-		assert 0
-
-
-def test_list2str():
-	assert isinstance(list2str([1, 2, 3,]), str)
-	if list2str([1, 2, 3]) == "1,2,3":
-		assert 1
-	else:
-		assert 0
-	
-	assert isinstance(list2str([1, 2, 3], sep=";"), str)  # tests with semicolon
-	if list2str((1, 2, 3), sep=";") == "1;2;3":
-		assert 1
-	else:
-		assert 0
 
-	assert isinstance(list2string([1, 2, 3, ]), str)
-	if list2string([1, 2, 3]) == "1,2,3":
-		assert 1
-	else:
-		assert 0
 
-	assert isinstance(list2string([1, 2, 3], sep=";"), str)  # tests with semicolon
-	if list2string((1, 2, 3), sep=";") == "1;2;3":
-		assert 1
-	else:
-		assert 0
-
 

tests/test_utils.py

@@ -0,0 +1,115 @@
+# -*- coding: utf-8 -*-
+"""
+test_utils
+~~~~~~~~~~~~~~~
+
+Test functions in utils.py
+
+"""
+
+import types
+
+import pytest
+
+from domdf_python_tools.utils import str2tuple, tuple2str, chunks, list2str, list2string, bdict
+
+
+def test_str2tuple():
+	assert isinstance(str2tuple("1,2,3"), tuple) # tests without spaces
+	assert isinstance(str2tuple("1, 2, 3"), tuple) # tests with spaces
+	assert isinstance(str2tuple("1; 2; 3", sep=";"), tuple) # tests with semicolon
+	if str2tuple("1,2,3") == (1, 2, 3):
+		assert 1
+	else:
+		assert 0
+		
+		
+def test_tuple2str():
+	assert isinstance(tuple2str(("1","2","3",)), str)
+	if tuple2str((1, 2, 3)) == "1,2,3":
+		assert 1
+	else:
+		assert 0
+		
+	assert isinstance(tuple2str((1,2,3,), sep=";"), str) # tests with semicolon
+	if tuple2str((1, 2, 3), sep=";") == "1;2;3":
+		assert 1
+	else:
+		assert 0
+
+
+def test_chunks():
+	assert isinstance(chunks(list(range(100)), 5), types.GeneratorType)
+	if list(chunks(list(range(100)), 5))[0] == [0,1,2,3,4]:
+		assert 1
+	else:
+		assert 0
+
+
+def test_list2str():
+	assert isinstance(list2str([1, 2, 3,]), str)
+	if list2str([1, 2, 3]) == "1,2,3":
+		assert 1
+	else:
+		assert 0
+	
+	assert isinstance(list2str([1, 2, 3], sep=";"), str)  # tests with semicolon
+	if list2str((1, 2, 3), sep=";") == "1;2;3":
+		assert 1
+	else:
+		assert 0
+	
+	assert isinstance(list2string([1, 2, 3, ]), str)
+	if list2string([1, 2, 3]) == "1,2,3":
+		assert 1
+	else:
+		assert 0
+	
+	assert isinstance(list2string([1, 2, 3], sep=";"), str)  # tests with semicolon
+	if list2string((1, 2, 3), sep=";") == "1;2;3":
+		assert 1
+	else:
+		assert 0
+
+
+def test_bdict():
+	new_dict = bdict(Alice=27, Bob=30, Dom=23)
+	
+	assert new_dict[23] == "Dom"
+	assert new_dict["Alice"] == 27
+	
+	
+def test_bdict_from_dict():
+	
+	original_dict = {"Alice": 27, "Bob": 30, "Dom": 23}
+	
+	new_dict = bdict(original_dict)
+	
+	assert new_dict[23] == "Dom"
+	assert new_dict["Alice"] == 27
+	
+	
+def test_bdict_from_zip():
+	
+	new_dict = bdict(zip(["Alice", "Bob", "Dom"], [27, 30, 23]))
+	
+	assert new_dict[23] == "Dom"
+	assert new_dict["Alice"] == 27
+
+
+def test_bdict_from_list():
+	new_dict = bdict([("Alice", 27), ("Bob", 30), ("Dom", 23)])
+	
+	assert new_dict[23] == "Dom"
+	assert new_dict["Alice"] == 27
+
+
+def test_bdict_errors():
+	new_dict = bdict([("Key1", "Value1"), ("Key2", "Value2"), ("Key3", "Value3")])
+	
+	with pytest.raises(ValueError):
+		new_dict["Key1"] = 1234
+	with pytest.raises(ValueError):
+		new_dict["Value1"] = 1234
+	new_dict["Key1"] = "Value1"
+	new_dict["Value1"] = "Key1"