[Sync Iteration] python/resistor-color-expert/4

solutions/python/resistor-color-expert/4/resistor_color_expert.py

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+"""
+Resistor Color Expert.
+
+In this exercise you will need to add tolerance to the mix.
+Tolerance is the maximum amount that a value can be above or
+below the main value. For example, if the last band is green,
+the maximum tolerance will be ±0.5%.
+"""
+
+# Mapping of resistor color names to their corresponding digit values.
+# pylint: disable=R0801
+COLOR_VALUES: dict[str, int] = {
+    "black": 0,
+    "brown": 1,
+    "red": 2,
+    "orange": 3,
+    "yellow": 4,
+    "green": 5,
+    "blue": 6,
+    "violet": 7,
+    "grey": 8,
+    "white": 9,
+}
+
+# Mapping of tolerance band color names to their maximum tolerance suffix.
+MAX_TOLERANCE: dict[str, str] = {
+    "grey": " ±0.05%",
+    "violet": " ±0.1%",
+    "blue": " ±0.25%",
+    "green": " ±0.5%",
+    "brown": " ±1%",
+    "red": " ±2%",
+    "gold": " ±5%",
+    "silver": " ±10%",
+}
+
+
+def resistor_label(colors: list[str]) -> str:
+    """
+    Return a human-readable resistor label from band colors.
+
+    Scales to the largest whole unit (ohms, kiloohms, megaohms, gigaohms)
+    and appends maximum tolerance if present.
+
+    :param colors: Band colors in order. Lengths:
+                   1 (value only);
+                   4 (two digits, multiplier, tolerance);
+                   5 (three digits, multiplier, tolerance).
+    :type colors: list[str]
+    :returns: Scaled value with units and optional tolerance (e.g., '4.7 kiloohms ±5%').
+    :rtype: str
+    :raises KeyError: If an unknown color is provided.
+    """
+    prefix: str = ""
+    postfix: str = ""
+    max_tolerance: str = ""
+
+    if len(colors) == 1:
+        prefix: str = f"{COLOR_VALUES[colors[0]]}"
+
+    if len(colors) == 4:
+        prefix: str = f"{COLOR_VALUES[colors[0]]}{COLOR_VALUES[colors[1]]}"
+        postfix = f"{'0' * COLOR_VALUES[colors[2]]}"
+        max_tolerance = MAX_TOLERANCE[colors[3]]
+
+    if len(colors) == 5:
+        prefix = (
+            f"{COLOR_VALUES[colors[0]]}"
+            f"{COLOR_VALUES[colors[1]]}"
+            f"{COLOR_VALUES[colors[2]]}"
+        )
+        postfix = f"{'0' * COLOR_VALUES[colors[3]]}"
+        max_tolerance = MAX_TOLERANCE[colors[4]]
+
+    int_val: int = int(prefix + postfix)
+
+    # Scale to the largest whole unit
+    # (ohms, kiloohms, megaohms, gigaohms) for readability
+    if 1000 <= int_val < 1000000:
+        return f"{float(int_val / 1000)}".rstrip(".0") + f" kiloohms{max_tolerance}"
+
+    if 1000000 <= int_val < 1000000000:
+        return f"{float(int_val / 1000000)}".rstrip(".0") + f" megaohms{max_tolerance}"
+
+    if 1000000000 <= int_val:
+        return f"{int_val / 1000000000}".rstrip(".0") + f" gigaohms{max_tolerance}"
+
+    return f"{int_val} ohms{max_tolerance}"