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R23-T058: Refactor resistor_color_code.py to share colour lookup and validation helpers #68

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R23-T058: Refactor resistor_color_code.py to share colour lookup and validation helpers #68

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132 changes: 67 additions & 65 deletions electronics/resistor_color_code.py
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,27 @@
}


def get_color_value[T](color: str, color_values: dict[str, T], band_name: str) -> T:
"""
Function returns the value stored for the color in color_values. It raises a
ValueError naming the band if the color is not allowed for that band. The
get_* functions below share this lookup and validation.

>>> get_color_value('Red', {'Red': 2}, 'example band')
2

>>> get_color_value('Aqua', {'Red': 2}, 'example band')
Traceback (most recent call last):
...
ValueError: Aqua is not a valid color for example band

"""
if color not in color_values:
msg = f"{color} is not a valid color for {band_name}"
raise ValueError(msg)
return color_values[color]


def get_significant_digits(colors: list) -> str:
"""
Function returns the digit associated with the color. Function takes a
Expand All @@ -149,13 +170,14 @@ def get_significant_digits(colors: list) -> str:
ValueError: Aqua is not a valid color for significant figure bands

"""
digit = ""
for color in colors:
if color not in significant_figures_color_values:
msg = f"{color} is not a valid color for significant figure bands"
raise ValueError(msg)
digit = digit + str(significant_figures_color_values[color])
return str(digit)
return "".join(
str(
get_color_value(
color, significant_figures_color_values, "significant figure bands"
)
)
for color in colors
)


def get_multiplier(color: str) -> float:
Expand All @@ -172,10 +194,7 @@ def get_multiplier(color: str) -> float:
ValueError: Ivory is not a valid color for multiplier band

"""
if color not in multiplier_color_values:
msg = f"{color} is not a valid color for multiplier band"
raise ValueError(msg)
return multiplier_color_values[color]
return get_color_value(color, multiplier_color_values, "multiplier band")


def get_tolerance(color: str) -> float:
Expand All @@ -192,10 +211,7 @@ def get_tolerance(color: str) -> float:
ValueError: Indigo is not a valid color for tolerance band

"""
if color not in tolerance_color_values:
msg = f"{color} is not a valid color for tolerance band"
raise ValueError(msg)
return tolerance_color_values[color]
return get_color_value(color, tolerance_color_values, "tolerance band")


def get_temperature_coeffecient(color: str) -> int:
Expand All @@ -212,10 +228,9 @@ def get_temperature_coeffecient(color: str) -> int:
ValueError: Cyan is not a valid color for temperature coeffecient band

"""
if color not in temperature_coeffecient_color_values:
msg = f"{color} is not a valid color for temperature coeffecient band"
raise ValueError(msg)
return temperature_coeffecient_color_values[color]
return get_color_value(
color, temperature_coeffecient_color_values, "temperature coeffecient band"
)


def get_band_type_count(total_number_of_bands: int, type_of_band: str) -> int:
Expand Down Expand Up @@ -277,19 +292,16 @@ def check_validity(number_of_bands: int, colors: list) -> bool:
ValueError: Cyan is not a valid color

"""
if number_of_bands >= 3 and number_of_bands <= 6:
if number_of_bands == len(colors):
for color in colors:
if color not in valid_colors:
msg = f"{color} is not a valid color"
raise ValueError(msg)
return True
else:
msg = f"Expecting {number_of_bands} colors, provided {len(colors)} colors"
raise ValueError(msg)
else:
msg = "Invalid number of bands. Resistor bands must be 3 to 6"
if not 3 <= number_of_bands <= 6:
raise ValueError("Invalid number of bands. Resistor bands must be 3 to 6")
if number_of_bands != len(colors):
msg = f"Expecting {number_of_bands} colors, provided {len(colors)} colors"
raise ValueError(msg)
for color in colors:
if color not in valid_colors:
msg = f"{color} is not a valid color"
raise ValueError(msg)
return True


def calculate_resistance(number_of_bands: int, color_code_list: list) -> dict:
Expand Down Expand Up @@ -331,41 +343,31 @@ def calculate_resistance(number_of_bands: int, color_code_list: list) -> dict:
ValueError: Lime is not a valid color

"""
is_valid = check_validity(number_of_bands, color_code_list)
if is_valid:
number_of_significant_bands = get_band_type_count(
number_of_bands, "significant"
)
significant_colors = color_code_list[:number_of_significant_bands]
significant_digits = int(get_significant_digits(significant_colors))
multiplier_color = color_code_list[number_of_significant_bands]
multiplier = get_multiplier(multiplier_color)
if number_of_bands == 3:
tolerance_color = None
else:
tolerance_color = color_code_list[number_of_significant_bands + 1]
tolerance = (
20 if tolerance_color is None else get_tolerance(str(tolerance_color))
)
if number_of_bands != 6:
temperature_coeffecient_color = None
else:
temperature_coeffecient_color = color_code_list[
number_of_significant_bands + 2
]
temperature_coeffecient = (
0
if temperature_coeffecient_color is None
else get_temperature_coeffecient(str(temperature_coeffecient_color))
)
resisitance = significant_digits * multiplier
if temperature_coeffecient == 0:
answer = f"{resisitance}Ω ±{tolerance}% "
else:
answer = f"{resisitance}Ω ±{tolerance}% {temperature_coeffecient} ppm/K"
return {"resistance": answer}
else:
if not check_validity(number_of_bands, color_code_list):
raise ValueError("Input is invalid")
number_of_significant_bands = get_band_type_count(number_of_bands, "significant")
significant_digits = int(
get_significant_digits(color_code_list[:number_of_significant_bands])
)
multiplier = get_multiplier(color_code_list[number_of_significant_bands])
# 3 band resistors have no tolerance band (default 20%); only 6 band resistors
# have a temperature coeffecient band (0 means "not present")
tolerance = (
get_tolerance(color_code_list[number_of_significant_bands + 1])
if number_of_bands >= 4
else 20
)
temperature_coeffecient = (
get_temperature_coeffecient(color_code_list[number_of_significant_bands + 2])
if number_of_bands == 6
else 0
)
resistance = significant_digits * multiplier
if temperature_coeffecient == 0:
answer = f"{resistance}Ω ±{tolerance}% "
else:
answer = f"{resistance}Ω ±{tolerance}% {temperature_coeffecient} ppm/K"
return {"resistance": answer}


if __name__ == "__main__":
Expand Down
42 changes: 42 additions & 0 deletions work/R23-T058/REFACTOR.md
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@@ -0,0 +1,42 @@
# R23-T058: refactor `electronics/resistor_color_code.py` (no behaviour change)

## What was duplicated
`get_multiplier`, `get_tolerance`, `get_temperature_coeffecient` and `get_significant_digits`
each repeated the same pattern: "if the colour is not in this band's table, build an
error message and raise ValueError, otherwise return the table value". `check_validity` and
`calculate_resistance` were deeply nested with `None` placeholders and an if/else that could never reach its `else`.

## What changed
1. **New shared helper** `get_color_value(color, color_values, band_name)`: the one place that does the lookup and raises `ValueError(f"{color} is not a valid color for {band_name}")`. The four `get_*` functions now call it with their own band name, so every error message is character-for-character the same as before (including the original "coeffecient" spelling).
2. **`check_validity`**: nested `if/if/for/else/else` replaced by guard clauses (same three errors, same order, same messages). Nesting depth 4 -> 2.
3. **`calculate_resistance`**: guard clause instead of `if is_valid: ... else:`; removed the `tolerance_color`/`temperature_coeffecient_color` `None` placeholders and the redundant `str(...)` wrappers; read the optional bands directly (`if number_of_bands >= 4` / `== 6`); fixed the local variable typo `resisitance` -> `resistance`.
4. Public names, signatures, tables and all 24 original doctests are untouched. Two doctests were added for the new helper (26 total).

## Complexity (McCabe, `ruff check --select C901 --config 'lint.mccabe.max-complexity = 0'`)
| function | before | after |
|---|---|---|
| get_color_value (new) | - | 2 |
| get_significant_digits | 3 | 1 |
| get_multiplier | 2 | 1 |
| get_tolerance | 2 | 1 |
| get_temperature_coeffecient | 2 | 1 |
| get_band_type_count | 3 | 3 |
| check_validity | **5** | **5** |
| calculate_resistance | **5** | **3** |
| total | 22 | 17 |

The worst functions before were `check_validity` and `calculate_resistance` (both 5).
`calculate_resistance` (the longest function: 35 -> 25 lines of code) is now 3.
`check_validity` stays at 5 because its three error conditions and the colour loop are inherent;
it is flatter and easier to read, but the score does not drop. (Repo config allows up to 17, so
`ruff check --select C90` passed before and after.)

## Behaviour proof
- `python -m doctest -v electronics/resistor_color_code.py`: 24 passed before; 26 passed after (24 original + 2 new).
- `work/R23-T058/equivalence_test.py` (60 tests) loads the **original** file and the **refactored** one and compares results and exception type + message on: every colour in every getter (valid, invalid, empty, wrong case, `None`, `int`), all band counts, 5,000 random `check_validity` calls, 20,000 random `calculate_resistance` calls, all 12^3 three-band and 12^4 four-band colour combinations, and one input per `raise` statement. All pass. A deliberate one-word change to an error message makes 7 of them fail, so the test does detect differences.
- Raise paths: all 10 `raise` statements remain. The last one (`raise ValueError("Input is invalid")` in `calculate_resistance`) can never run, because `check_validity` returns True or raises; it was kept so behaviour and the raise count are unchanged.

## Coverage
Baseline and after output are in `coverage_before.txt` / `coverage_after.txt`. The same three statements are
uncovered before and after: the unreachable `raise ValueError("Input is invalid")` and the two lines of the
`if __name__ == "__main__":` block. The refactor reduced the file's statement count (about 74 -> 54 by a line tracer) without losing coverage.
9 changes: 9 additions & 0 deletions work/R23-T058/complexity_after.txt
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electronics/resistor_color_code.py:138:5: C901 `get_color_value` is too complex (2 > 0)
electronics/resistor_color_code.py:159:5: C901 `get_significant_digits` is too complex (1 > 0)
electronics/resistor_color_code.py:183:5: C901 `get_multiplier` is too complex (1 > 0)
electronics/resistor_color_code.py:200:5: C901 `get_tolerance` is too complex (1 > 0)
electronics/resistor_color_code.py:217:5: C901 `get_temperature_coeffecient` is too complex (1 > 0)
electronics/resistor_color_code.py:236:5: C901 `get_band_type_count` is too complex (3 > 0)
electronics/resistor_color_code.py:275:5: C901 `check_validity` is too complex (5 > 0)
electronics/resistor_color_code.py:307:5: C901 `calculate_resistance` is too complex (3 > 0)
Found 8 errors.
8 changes: 8 additions & 0 deletions work/R23-T058/complexity_before.txt
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electronics/resistor_color_code.py:138:5: C901 `get_significant_digits` is too complex (3 > 0)
electronics/resistor_color_code.py:161:5: C901 `get_multiplier` is too complex (2 > 0)
electronics/resistor_color_code.py:181:5: C901 `get_tolerance` is too complex (2 > 0)
electronics/resistor_color_code.py:201:5: C901 `get_temperature_coeffecient` is too complex (2 > 0)
electronics/resistor_color_code.py:221:5: C901 `get_band_type_count` is too complex (3 > 0)
electronics/resistor_color_code.py:260:5: C901 `check_validity` is too complex (5 > 0)
electronics/resistor_color_code.py:295:5: C901 `calculate_resistance` is too complex (5 > 0)
Found 7 errors.
53 changes: 53 additions & 0 deletions work/R23-T058/coverage_after.txt
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============================= test session starts ==============================
platform darwin -- Python 3.13.18, pytest-9.2.0, pluggy-1.7.0 -- /Users/paulamibhosle/TheAlgorithms-Python/.venv/bin/python
cachedir: .pytest_cache
hypothesis profile 'default'
rootdir: /Users/paulamibhosle/TheAlgorithms-Python
configfile: pyproject.toml
plugins: hypothesis-6.170.15, cov-7.1.0
collecting ... collected 8 items

electronics/resistor_color_code.py::electronics.resistor_color_code.calculate_resistance PASSED [ 12%]
electronics/resistor_color_code.py::electronics.resistor_color_code.check_validity PASSED [ 25%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_band_type_count PASSED [ 37%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_color_value PASSED [ 50%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_multiplier PASSED [ 62%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_significant_digits PASSED [ 75%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_temperature_coeffecient PASSED [ 87%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_tolerance PASSED [100%]

================================ tests coverage ================================
______________ coverage: platform darwin, python 3.13.18-final-0 _______________

Name Stmts Miss Cover Missing
----------------------------------------------------------------------
electronics/apparent_power.py 11 11 0% 1-37
electronics/builtin_voltage.py 18 18 0% 1-66
electronics/capacitor_equivalence.py 20 20 0% 3-53
electronics/carrier_concentration.py 20 20 0% 5-75
electronics/charging_capacitor.py 12 12 0% 18-72
electronics/charging_inductor.py 12 12 0% 29-97
electronics/circular_convolution.py 26 26 0% 15-98
electronics/coulombs_law.py 24 24 0% 3-85
electronics/electric_conductivity.py 19 19 0% 1-73
electronics/electric_power.py 20 20 0% 2-59
electronics/electrical_impedance.py 15 15 0% 7-46
electronics/full_wave_rectifier.py 27 27 0% 1-130
electronics/half_wave_rectifier.py 27 27 0% 1-130
electronics/ic_555_timer.py 13 13 0% 1-75
electronics/ind_reactance.py 21 21 0% 2-69
electronics/ohms_law.py 16 16 0% 2-42
electronics/power_factor_correction.py 23 23 0% 4-125
electronics/real_and_reactive_power.py 12 12 0% 1-49
electronics/resistor_equivalence.py 20 20 0% 3-56
electronics/resonant_frequency.py 11 11 0% 11-49
electronics/star_delta_conversions.py 25 25 0% 5-103
electronics/wheatstone_bridge.py 8 8 0% 2-72
electronics/resistor_color_code.py 54 3 94% 347, 374-376
electronics/__init__.py 0 0 100%
----------------------------------------------------------------------
TOTAL 454 403 11%
============================= slowest 10 durations =============================

(10 durations < 0.005s hidden. Use -vv to show these durations.)
============================== 8 passed in 0.14s ===============================
52 changes: 52 additions & 0 deletions work/R23-T058/coverage_before.txt
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============================= test session starts ==============================
platform darwin -- Python 3.13.18, pytest-9.2.0, pluggy-1.7.0 -- /Users/paulamibhosle/TheAlgorithms-Python/.venv/bin/python
cachedir: .pytest_cache
hypothesis profile 'default'
rootdir: /Users/paulamibhosle/TheAlgorithms-Python
configfile: pyproject.toml
plugins: hypothesis-6.170.15, cov-7.1.0
collecting ... collected 7 items

electronics/resistor_color_code.py::electronics.resistor_color_code.calculate_resistance PASSED [ 14%]
electronics/resistor_color_code.py::electronics.resistor_color_code.check_validity PASSED [ 28%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_band_type_count PASSED [ 42%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_multiplier PASSED [ 57%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_significant_digits PASSED [ 71%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_temperature_coeffecient PASSED [ 85%]
electronics/resistor_color_code.py::electronics.resistor_color_code.get_tolerance PASSED [100%]

================================ tests coverage ================================
______________ coverage: platform darwin, python 3.13.18-final-0 _______________

Name Stmts Miss Cover Missing
----------------------------------------------------------------------
electronics/apparent_power.py 11 11 0% 1-37
electronics/builtin_voltage.py 18 18 0% 1-66
electronics/capacitor_equivalence.py 20 20 0% 3-53
electronics/carrier_concentration.py 20 20 0% 5-75
electronics/charging_capacitor.py 12 12 0% 18-72
electronics/charging_inductor.py 12 12 0% 29-97
electronics/circular_convolution.py 26 26 0% 15-98
electronics/coulombs_law.py 24 24 0% 3-85
electronics/electric_conductivity.py 19 19 0% 1-73
electronics/electric_power.py 20 20 0% 2-59
electronics/electrical_impedance.py 15 15 0% 7-46
electronics/full_wave_rectifier.py 27 27 0% 1-130
electronics/half_wave_rectifier.py 27 27 0% 1-130
electronics/ic_555_timer.py 13 13 0% 1-75
electronics/ind_reactance.py 21 21 0% 2-69
electronics/ohms_law.py 16 16 0% 2-42
electronics/power_factor_correction.py 23 23 0% 4-125
electronics/real_and_reactive_power.py 12 12 0% 1-49
electronics/resistor_equivalence.py 20 20 0% 3-56
electronics/resonant_frequency.py 11 11 0% 11-49
electronics/star_delta_conversions.py 25 25 0% 5-103
electronics/wheatstone_bridge.py 8 8 0% 2-72
electronics/resistor_color_code.py 74 3 96% 368, 372-374
electronics/__init__.py 0 0 100%
----------------------------------------------------------------------
TOTAL 474 403 15%
============================= slowest 10 durations =============================

(10 durations < 0.005s hidden. Use -vv to show these durations.)
============================== 7 passed in 0.14s ===============================
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