diff --git a/strings/string_switch_case.py b/strings/string_switch_case.py
new file mode 100644
index 000000000..9a07472df
--- /dev/null
+++ b/strings/string_switch_case.py
@@ -0,0 +1,108 @@
+import re
+
+"""
+general info:
+https://en.wikipedia.org/wiki/Naming_convention_(programming)#Python_and_Ruby
+
+pascal case [ an upper Camel Case ]: https://en.wikipedia.org/wiki/Camel_case
+
+camel case: https://en.wikipedia.org/wiki/Camel_case
+
+kebab case [ can be found in general info ]:
+https://en.wikipedia.org/wiki/Naming_convention_(programming)#Python_and_Ruby
+
+snake case: https://en.wikipedia.org/wiki/Snake_case
+"""
+
+
+# assistant functions
+def split_input(str_: str) -> list:
+    """
+    >>> split_input("one two 31235three4four")
+    [['one', 'two', '31235three4four']]
+    """
+    return [char.split() for char in re.split(r"[^ a-z A-Z 0-9 \s]", str_)]
+
+
+def to_simple_case(str_: str) -> str:
+    """
+    >>> to_simple_case("one two 31235three4four")
+    'OneTwo31235three4four'
+    """
+    string_split = split_input(str_)
+    return "".join(
+        ["".join([char.capitalize() for char in sub_str]) for sub_str in string_split]
+    )
+
+
+def to_complex_case(text: str, upper: bool, separator: str) -> str:
+    """
+    >>> to_complex_case("one two 31235three4four", True, "_")
+    'ONE_TWO_31235THREE4FOUR'
+    >>> to_complex_case("one two 31235three4four", False, "-")
+    'one-two-31235three4four'
+    """
+    try:
+        string_split = split_input(text)
+        if upper:
+            res_str = "".join(
+                [
+                    separator.join([char.upper() for char in sub_str])
+                    for sub_str in string_split
+                ]
+            )
+        else:
+            res_str = "".join(
+                [
+                    separator.join([char.lower() for char in sub_str])
+                    for sub_str in string_split
+                ]
+            )
+        return res_str
+    except IndexError:
+        return "not valid string"
+
+
+# main content
+def to_pascal_case(text: str) -> str:
+    """
+    >>> to_pascal_case("one two 31235three4four")
+    'OneTwo31235three4four'
+    """
+    return to_simple_case(text)
+
+
+def to_camel_case(text: str) -> str:
+    """
+    >>> to_camel_case("one two 31235three4four")
+    'oneTwo31235three4four'
+    """
+    try:
+        res_str = to_simple_case(text)
+        return res_str[0].lower() + res_str[1:]
+    except IndexError:
+        return "not valid string"
+
+
+def to_snake_case(text: str, upper: bool) -> str:
+    """
+    >>> to_snake_case("one two 31235three4four", True)
+    'ONE_TWO_31235THREE4FOUR'
+    >>> to_snake_case("one two 31235three4four", False)
+    'one_two_31235three4four'
+    """
+    return to_complex_case(text, upper, "_")
+
+
+def to_kebab_case(text: str, upper: bool) -> str:
+    """
+    >>> to_kebab_case("one two 31235three4four", True)
+    'ONE-TWO-31235THREE4FOUR'
+    >>> to_kebab_case("one two 31235three4four", False)
+    'one-two-31235three4four'
+    """
+    return to_complex_case(text, upper, "-")
+
+
+if __name__ == "__main__":
+    __import__("doctest").testmod()