1 files changed, 58 insertions, 0 deletions
diff --git a/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py b/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py
new file mode 100644
index 000000000..08c1b0ea5
--- /dev/null
+++ b/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py
@@ -0,0 +1,58 @@
+"""Assertions for runtime type checking of function arguments."""
+
+from typing import Any
+
+
+def assert_is_string(value: Any, name: str) -> None:
+    """If :param value: isn't of type str, raise a TypeError.
+
+    >>> try: assert_is_string(123, 'var')
+    ... except TypeError as type_error: print(str(type_error))
+    ...
+    expected variable 'var', with value 123, to have type 'str', not 'int'
+    """
+    if not isinstance(value, str):
+        raise TypeError(
+            f"expected variable '{name}', with value {str(value)}, to have"
+            + f" type 'str', not '{type(value).__name__}'"
+        )
+
+
+def assert_is_list(value: Any, name: str) -> None:
+    """If :param value: isn't of type list, raise a TypeError.
+
+    >>> try: assert_is_list(123, 'var')
+    ... except TypeError as type_error: print(str(type_error))
+    ...
+    expected variable 'var', with value 123, to have type 'list', not 'int'
+    """
+    if not isinstance(value, list):
+        raise TypeError(
+            f"expected variable '{name}', with value {str(value)}, to have"
+            + f" type 'list', not '{type(value).__name__}'"
+        )
+
+
+def assert_is_int(value: Any, name: str) -> None:
+    """If :param value: isn't of type int, raise a TypeError.
+
+    >>> try: assert_is_int('asdf', 'var')
+    ... except TypeError as type_error: print(str(type_error))
+    ...
+    expected variable 'var', with value asdf, to have type 'int', not 'str'
+    """
+    if not isinstance(value, int):
+        raise TypeError(
+            f"expected variable '{name}', with value {str(value)}, to have"
+            + f" type 'int', not '{type(value).__name__}'"
+        )
+
+
+def assert_is_hex_string(value: Any, name: str) -> None:
+    """Assert that :param value: is a string of hex chars.
+
+    If :param value: isn't a str, raise a TypeError.  If it is a string but
+    contains non-hex characters ("0x" prefix permitted), raise a ValueError.
+    """
+    assert_is_string(value, name)
+    int(value, 16)  # raises a ValueError if value isn't a base-16 str