loop file

Author: willmcgugan

src/textual/_loop.py

@@ -0,0 +1,43 @@
+from typing import Iterable, Tuple, TypeVar
+
+T = TypeVar("T")
+
+
+def loop_first(values: Iterable[T]) -> Iterable[Tuple[bool, T]]:
+    """Iterate and generate a tuple with a flag for first value."""
+    iter_values = iter(values)
+    try:
+        value = next(iter_values)
+    except StopIteration:
+        return
+    yield True, value
+    for value in iter_values:
+        yield False, value
+
+
+def loop_last(values: Iterable[T]) -> Iterable[Tuple[bool, T]]:
+    """Iterate and generate a tuple with a flag for last value."""
+    iter_values = iter(values)
+    try:
+        previous_value = next(iter_values)
+    except StopIteration:
+        return
+    for value in iter_values:
+        yield False, previous_value
+        previous_value = value
+    yield True, previous_value
+
+
+def loop_first_last(values: Iterable[T]) -> Iterable[Tuple[bool, bool, T]]:
+    """Iterate and generate a tuple with a flag for first and last value."""
+    iter_values = iter(values)
+    try:
+        previous_value = next(iter_values)
+    except StopIteration:
+        return
+    first = True
+    for value in iter_values:
+        yield first, False, previous_value
+        first = False
+        previous_value = value
+    yield first, True, previous_value