feat: minor regex and casting tests

.editorconfig

@@ -9,7 +9,7 @@ insert_final_newline = true
 charset = utf-8
 
 [*.py]
-indent_style = tab
+indent_style = space
 indent_size = 4
 
 [Makefile]

Makefile

@@ -7,7 +7,7 @@ save:
 	pip freeze > requirements.txt
 
 run:
-	python src/main.py
+	python src/main.py $(MODULE)
 
 test:
 	python -m pytest -v

README.rst

@@ -2,3 +2,10 @@ Python by example
 =================
 
 The intention of this repository is to teach me the basics, along with the best or common practiced, of python development.
+
+Modules must include a "run" function in order to be executed as a dynamic import.
+
+To run
+======
+
+`$ make MODULE="module submodule" run`

requirements.txt

@@ -1,8 +1,10 @@
 iniconfig==2.1.0
 mpmath==1.3.0
+narwhals==2.25.0
 numpy==2.3.3
 packaging==25.0
 pandas==2.3.3
+plotly==6.9.0
 pluggy==1.6.0
 Pygments==2.19.2
 pytest==8.4.2

src/main.py

@@ -1,20 +1,15 @@
-from sympy import diff, limit, oo, symbols
+import sys
-import unittest
 
-from modules.math import (
+if __name__ == "__main__":
-	test_math_module
+    if sys.argv.__len__() < 2:
-)
+        print("[ERROR] Module name must be specified as an argument:")
-from modules.probability import (
+        print(" $ python src/main.py <module_name>")
-	test_probability_module
+        exit(-1)
-)
-from modules.statistics import (
-	test_statistics_module
-)
-from modules.strings import t_strings
 
-if __name__=="__main__":
+    module_name = sys.argv[1]
-	# t_strings()
+    module_path = "modules."+module_name
-	# test_math_module()
+    if sys.argv.__len__() > 2:
-	# test_probability_module()
+        for submodule_name in sys.argv[2:]:
-	# test_statistics_module()
+            module_path += "."+submodule_name
-	# test_exercises_module()
+    module_selected = __import__(module_path, fromlist=[""])
+    module_selected.run()

src/modules/backend/server.py

@@ -0,0 +1,2 @@
+def run():
+    print("The server will start here")

src/modules/essential_math/math.py

@@ -1,6 +1,6 @@
-## This module represents the first chapter of the book 
+## This module represents the first chapter of the book
 ##  "Essential Math for Data Science" - Thomas Nield
-##  Chaper 1 - Basic Math and Calculus Review 
+##  Chaper 1 - Basic Math and Calculus Review
 
 from cmath import log as complex_log  # used for complex numbers
 from math import e, exp, log
@@ -90,7 +90,7 @@ def t_approximate_integral(f, init, end, precission):
 def t_calculate_integral(f, init, end, symbol):
     return integrate(f, (symbol, init, end))
 
-def test_math_module():
+def run():
 	print("=== Math module ===")
 	t_exponent(2,8)
 	print(t_compound_interest(100, 20 / 100, 2, 12))

src/modules/essential_math/probability.py

@@ -1,6 +1,6 @@
-## This module represents the second chapter of the book 
+## This module represents the second chapter of the book
 ##  "Essential Math for Data Science" - Thomas Nield
-##  Chapter 2 - Probability 
+##  Chapter 2 - Probability
 
 from scipy.stats import binom, beta
 from math import factorial
@@ -31,7 +31,7 @@ class BinomialDistribution:
 		# For each number calc the probability of that exact number of outcomes (no order)
 		for k in range(n + 1):
 			# 1. Simple combinatory with the binomial coeficient (combinations of k elements out of a pool of n without repetition without order)
-			combinatory = BinomialDistribution.binomial_coeficient(n, k)	
+			combinatory = BinomialDistribution.binomial_coeficient(n, k)
 			# 2. Probability of success, the probability of making it k times
 			probability_of_success = p ** k
 			# 3. Probability of failure, inverse of the success
@@ -44,14 +44,14 @@ class BinomialDistribution:
 # > Returns a continuous function, so the final probability of X or better must be calculated using integrals (the area under the curve)
 class BetaDistribution:
 	@staticmethod
-	def calc(probability, success_count, failure_count):	
+	def calc(probability, success_count, failure_count):
 		# Only calcs the rpbability to the left
 		return beta.cdf(probability, success_count, failure_count)
 
 	@staticmethod
 	def calc_right(probability, success_count, failure_count):
 		return 1.0 - BetaDistribution.calc(probability, success_count, failure_count)
-	
+
 	@staticmethod
 	def calc_region(init_probability, end_probability, success_count, failure_count):
 		return BetaDistribution.calc(end_probability, success_count, failure_count) - BetaDistribution.calc(init_probability, success_count, failure_count)
@@ -63,7 +63,7 @@ class Exercises:
 	def one():
 		# 30% change of rain and 40% change your umbrella order will arrive. P(R AND U)
 		return p_r * p_u
-	
+
 	@staticmethod
 	def two():
 		# Same Ps as previous. P(!R OR U)
@@ -81,7 +81,7 @@ class Exercises:
 		p_bail = 0.4
 		p_at_least_50_bail = 0.0
 		for x in range(50, n + 1):
-			p_at_least_50_bail += binom.pmf(x, n, p_bail) 
+			p_at_least_50_bail += binom.pmf(x, n, p_bail)
 		return p_at_least_50_bail
 
 	@staticmethod
@@ -91,7 +91,7 @@ class Exercises:
 		t = 2
 		return  1.0 - BetaDistribution.calc(0.5, 8, 2)
 
-	
+
 	@staticmethod
 	def test():
 		print("P(R AND U) = {0}".format(Exercises.one()))
@@ -101,7 +101,7 @@ class Exercises:
 		print("P(fair) = {0}".format(Exercises.five()))
 
 
-def test_probability_module():
+def run():
 	print("=== Probability module ===")
 	print(">> Binomial distribution")
 	BinomialDistribution.example()

src/modules/essential_math/statistics.py

@@ -0,0 +1,275 @@
+## This module represents the third chapter of the book
+##  "Essential Math for Data Science" - Thomas Nield
+##  Chapter 3 - Statistics
+
+from math import sqrt, pi, e, exp
+from scipy.stats import norm, t
+
+import random
+import plotly.express as px
+
+
+def my_mean(list):
+    return sum(list) / len(list)
+
+
+def weighted_mean(items, weights):
+    if (len(items) != len(weights)):
+        return
+    total = 0
+    for i in range(len(items)):
+        total += items[i] * weights[i]
+    return total / sum(weights)
+
+
+def weighted_mean_inline(items, weights):
+    return sum(s * w for s, w in zip(items, weights)) / sum(weights)
+
+
+# also called 50% quantile
+def median(items):
+    ordered = sorted(items)
+    length = len(ordered)
+    pair = length % 2 == 0
+    mid = int(length / 2) - 1 if pair else int(length/2)
+
+    if pair:
+        return (ordered[mid] + ordered[mid+1]) / 2
+    else:
+        return ordered[mid]
+
+
+def mode(items):
+    sums = []
+
+
+def population_variance(value_list, mean):
+    summatory = 0.0
+    for value in value_list:
+        summatory += (value - mean) ** 2
+    return summatory / len(value_list)
+
+
+def population_variance_inline(value_list):
+    return sum((v - (sum(value_list) / len(value_list))) ** 2 for v in value_list) / len(value_list)
+
+
+def sample_variance(value_list):
+    mean = sum(value_list) / len(value_list)
+    return sum((value - mean) ** 2 for value in value_list) / (len(value_list) - 1)
+
+
+def population_standard_deviation(value_list):
+    return sqrt(population_variance_inline(value_list))
+
+
+def sample_standard_deviation(value_list):
+    return sqrt(sample_variance(value_list))
+
+
+def standard_deviation(value_list, is_sample):
+    return sample_standard_deviation(value_list) if is_sample else population_standard_deviation(value_list)
+
+
+# Normal distribution
+# PDF generates the Normal Distribution (symetric arround the mean)
+def normal_probability_density_function(x: float, mean: float, standard_deviation: float):
+    return (1.0 / (2.0 * pi * standard_deviation ** 2) ** 0.5) * exp(-1.0 * ((x - mean) ** 2 / (2.0 * standard_deviation ** 2)))
+
+
+def normal_cumulative_density_function(x, mean, std_deviation):
+    return norm.cdf(x, mean, std_deviation)
+
+
+# Check exected value for a given probability
+def inverse_cumulative_density_function(prob, mean, std_dev):
+    x = norm.ppf(prob, mean, std_dev)
+    return x
+
+
+# Z-scores are valuable in order to normalize 2 pieces of data
+def z_score(value, data_mean, std_deviation):
+    return (value - data_mean) / std_deviation
+
+
+def coeficient_of_variation(std_deviation, mean):
+    return (std_deviation / mean)
+
+
+def test_central_limit_theorem(sample_size, sample_count):
+    x_values = [(sum([random.uniform(0.0,1.0) for i in range(sample_size)]) / sample_size) for _ in range(sample_count)]
+    y_values = [1 for _ in range(sample_count)]
+    px.histogram(x=x_values, y=y_values, nbins=20).show()
+
+
+def generic_critical_z_value(probability):
+    norm_dist = norm(loc=0.0, scale=1.0)
+    left_tail_area = (1.0 - probability) / 2.0
+    upper_area = 1.0 - ((1.0 - probability) / 2.0)
+    return norm_dist.ppf(left_tail_area), norm_dist.ppf(upper_area)
+
+
+def margin_of_error(sample_size, standard_deviation, z_value):
+    return z_value * (standard_deviation / sqrt(sample_size)) # +-, we return the one provided by the z_value (tail or upper)
+
+
+# How confident we are at a population metric given a sample (the interval we are "probability" sure the value will be)
+def confidence_interval(probability, sample_size, standard_deviation, z_value, mean):
+    critical_z = generic_critical_z_value(probability)
+    margin_error = margin_of_error(sample_size, standard_deviation, z_value)
+    return mean + margin_error, mean - margin_error
+
+
+# T Distribution
+# Similar to the normal distribution but made for smaller sample-sizes (30 or less)
+# When we get close to the 31 items, both are identical
+def get_critical_value_range_t(conficence_percentage: float, sample_size: int):
+    untrusted_percentage = 1.0 - conficence_percentage
+    lower = t.ppf(untrusted_percentage / 2, df=sample_size-1)
+    upper = t.ppf(conficence_percentage + (untrusted_percentage / 2), df=sample_size-1)
+    return (lower, upper)
+
+
+def run():
+    print("=== Statistics module ===")
+
+    list = [ 1, 2, 3, 4, 5, 6]
+    print(">> The mean of {0} is {1}".format(list, my_mean(list)))
+
+    weights = [0.2, 0.5, 0.7, 1, 0, 0.9]
+    print(">> The weighted_mean of {0} is {1} and it is equivalent to {2}".format(list, weighted_mean(list, weights), weighted_mean_inline(list, weights)))
+
+    print(">> The median is {0}".format(median(list)))
+
+    values = [ 0, 1, 5, 7, 9, 10, 14]
+    _population_variance = population_variance(values, sum(values) / len(values))
+    population_variance_calc_inline = population_variance_inline(values);
+    print("The population variance is", _population_variance, population_variance_calc_inline)
+
+    std_dev = standard_deviation(values, False)
+    print("The standard deviation is", std_dev)
+
+    sample = values.copy()
+    del sample[3]
+    del sample[1]
+    print("The sample variance for a population is", sample_variance(sample))
+    print("The standard deviation for a population is", standard_deviation(sample, True))
+
+    print("== Normal distribution ==")
+
+    values = [ 0, 1, 5, 7, 9, 10, 14]
+    mean = sum(values) / len(values)
+    std_dev = standard_deviation(values, False)
+    target_x = 1
+
+    print(">> The probability_density_function for x = 1 over the example data is {0}".format(normal_probability_density_function(target_x, mean, std_dev)))
+
+    print(">> The probability for observing a value smaller than 1 is given by the cumulative density function and it is: {0}".format(normal_cumulative_density_function(target_x, mean, std_dev)))
+
+    target_probability = 0.5
+    expected_value = inverse_cumulative_density_function(target_probability, mean, std_dev);
+    print(">> For a probability of .5 we expect the value: ", expected_value)
+
+    # Population with cold MEAN recovery time of 18 days, with std_dev of 1.5 days.
+    # Chances of recovery between 15 and 21 days
+    mean = 18
+    std_dev = 1.5
+    init = 15
+    end = 21
+    chances = normal_cumulative_density_function(end, mean, std_dev) - normal_cumulative_density_function(init, mean, std_dev)
+    print("Chances of recovering from a cold between 15 and 21 days: ", chances)
+    print("Chances of recovering before 15 days or after 21: ", 1.0 - chances)
+    # since its a normal distribution, the chances are equaly distributed
+    print("Chances of recovering before 15 days: ", (1.0 - chances) / 2)
+
+    # Apply rug (or drug) to 40 people and see a 16 MEAN recovery time. Test if rug improved mean or casuality
+    ## One tailed atest: use inverse cdf in order to find the limit value for a given %.
+    new_mean = 16
+    min_target_percentage = 0.05 # this is a standard
+    min_mean = inverse_cumulative_density_function(min_target_percentage, mean, std_dev)
+    if (min_mean < new_mean):
+        print("The rug (drug) did nothing.")
+    else:
+        print("The rug (drug) worked.")
+    ## One tailed test with a P value
+    p_value = normal_cumulative_density_function(new_mean, mean, std_dev)
+    if (p_value > min_target_percentage):
+        print("The rug (drug) did nothing.")
+    else:
+        print("The rug (drug) worked.")
+
+    ## Two tailed test (look for both sides of the normal distribution)
+    ## Double the checks, harder to prove (x2) and checks if the rug(drug) makes the recovery time worse.
+    left_min_target = min_target_percentage / 2
+    x1 = inverse_cumulative_density_function(left_min_target, mean, std_dev)
+    x2 = inverse_cumulative_density_function(1.0 - left_min_target, mean, std_dev)
+    if (new_mean < x1 or new_mean > x2):
+        print("The rug (drug) worked.", x1, x2)
+    else:
+        print("The rug (drug) did nothing.", x1, x2)
+    ## Two tailed test with a P value
+    p1 = normal_cumulative_density_function(new_mean, mean, std_dev)
+    right_symetrical_mean = mean + (mean - new_mean)
+    p2 = 1.0 - normal_cumulative_density_function(right_symetrical_mean, mean, std_dev)
+    p_value = p1 + p2
+    if (p_value < min_target_percentage):
+        print("The rug (drug) worked.", p_value)
+    else:
+        print("The rug (drug) did nothing.", p_value)
+    #### CONCEPT: P-hacking, searching for data (in big data scenarios) that passes the p_value < 0.05 test and claiming for a relation.
+
+    print("== Z-scores ==")
+
+    print("A house (A) of 150K in a neighborhood of 140K mean and 3K std_dev has a Z-score: {0}".format(z_score(150000, 140000, 3000)))
+    print("A house (B) of 815K in a neighborhood of 800K mean and 10K std_dev has a Z-score: {0}".format(z_score(815000, 800000, 10000)))
+    print("The House A is much more expensive because its z-score is higher.")
+    print("The neighborhood of B has a coeficient of variation: {0}, and the one of A: {1}".format(coeficient_of_variation(3000, 140000), coeficient_of_variation(10000, 800000)))
+    print("This means that the neighborhood of A has more spread in its prices")
+
+    print("== Central Limit Theorem ==")
+    test_central_limit_theorem(sample_size=1, sample_count=1000)
+    test_central_limit_theorem(sample_size=31, sample_count=1000)
+
+    print("== T Distribution ==")
+    confidence = 0.95
+    sample_size = 25
+    (lower, upper) = get_critical_value_range_t(confidence, sample_size)
+    print("The confidence interval is: ", lower, upper)
+
+    print("== Final Exercises ==")
+    # 1.
+    pool_widths = (1.78, 1.75, 1.72, 1.74, 1.77)
+    pool_width_mean = my_mean(pool_widths)
+    pool_width_std = standard_deviation(pool_widths, True)
+    print("1: ", pool_width_mean, pool_width_std)
+
+    # 2.
+    z_mean = 42
+    z_std_dev = 8
+    z_prob_init = 20
+    z_prob_end = 30
+    z_prob_final = normal_cumulative_density_function(z_prob_end,z_mean,z_std_dev) - normal_cumulative_density_function(z_prob_init, z_mean, z_std_dev)
+    print("2: ", z_prob_final)
+
+    # 3.
+    filament_value = 1.75
+    filament_sample_size = 34
+    filament_mean = 1.715588
+    filament_std_dev = 0.029252
+    filament_percentage_conficence = .99
+    filament_z_value = z_score(filament_value,filament_mean, filament_std_dev)
+    (filament_confidence_init, filament_conficence_end) = confidence_interval(filament_percentage_conficence, filament_sample_size, filament_std_dev, filament_z_value, filament_mean)
+    print("3: ", filament_confidence_init, filament_conficence_end)
+
+    # 4.
+    original_sales_average = 10345
+    original_sales_std_dev = 552
+    new_sales_average = 11641
+    min_sales_percentage = 0.05
+
+    sales_p1 = 1.0 - normal_cumulative_density_function(new_sales_average, original_sales_average, original_sales_std_dev)
+    sales_p = sales_p1 * 2 # take advantage of symmetry
+    if (sales_p < min_sales_percentage):
+        print("The sales campaing worked", sales_p)
+    else:
+        print("The sales campaing did NOT work")

src/modules/exercises/essentials.py

@@ -1,3 +1,7 @@
+def run():
+    print("! This module is ran through tests, do not expect an output.")
+
+
 def maximum_subarray_sum(input_array: list[int]):
 	max_sum = input_array[0]
 	subarray = [input_array[0]]
@@ -20,3 +24,32 @@ def find_missing(input_aray: list[int]):
 	return sum(get_array_range(1, len(input_aray) + 1)) - sum(input_aray)
 
 def trap_rain_water(input_aray: list[int]):
+	ceiling = max(input_aray)
+	# Step 1: create a matrix with the graph
+	container = []
+	for wall_index in range(0, len(input_aray)):
+		wall = []
+		for coord_index in range(0, ceiling):
+			if (coord_index < input_aray[wall_index]):
+				wall.insert(coord_index, "w")
+			else:
+				wall.insert(coord_index, "a")
+		container.insert(wall_index, wall)
+
+	total_water = 0
+	# Step 2: fill the air with water
+	for wall_x in range(0, len(input_aray)):
+		for wall_y in range(0, input_aray[wall_x]):
+			if (container[wall_x][wall_y] == "a"):
+				continue
+			# Step 2.1 count distance with next wall
+			temp_water = 0
+			for water_x in range(wall_x + 1, len(input_aray)):
+				if (container[water_x][wall_y] == "a"):
+					temp_water += 1
+				else:
+					total_water += temp_water
+					break
+
+	return total_water
+

src/modules/primitives/casting.py

@@ -0,0 +1,6 @@
+def run():
+    print("== Type casting ==")
+
+    value = "1234"
+    value_int = int(value)
+    print(f"{type(value)} value: {value + str(5)} and {type(value_int)} value: {value_int + 5}")

src/modules/primitives/regex.py

@@ -0,0 +1,16 @@
+import re
+
+
+def run():
+    print("== Regular expressions ==")
+
+    test_txt = "This is a long test with more test 1234"
+
+    matched = re.search("test", test_txt)
+    print(f"Found span: {matched.span()}, as a group: {matched.group()}")
+
+    matched_all = re.findall("^test$", test_txt)
+    print(f"Found all: {matched_all}")
+
+    replaced = re.sub("[(is)*|(it)*]+", "x", test_txt, 7)
+    print(f"Repalced at: {test_txt} as: {replaced}")

src/modules/primitives/strings.py

@@ -0,0 +1,84 @@
+from string import Formatter
+
+def template_strings():
+    my_template = "This is a value: {test}"
+    print(my_template.format(test="another"))
+
+    complext_template = "The number of days in a %s is %d"
+    # % is the string formatting operator
+    print(complext_template % ("year", 365))
+
+    print("Numbers can also be formatted, such as %.2f" % 123.1235)
+
+    print("Simple template values can also be indexed {0} {1} but CANT use the formatting operator '%'".format("first", "second"))
+
+    print("What can do is specify both a template value name and a format, such as {test:.2f}".format(test=123.12345))
+
+    name = "Me"
+    surname = "Another dude"
+    print(f"I'm {name} {surname}")
+
+    # Lower level access to format flows
+    test_template = "This is an example with {with_quotes!r} or a number {num:.2f}"
+    for text, field, format_spec, conversion  in Formatter().parse(test_template):
+        print(f"{text=}, {field=}, {format_spec=}, {conversion=}")
+
+    # Allow input in templates
+    # These are only used to properly manage templates on code, such as library imput for better validation
+    #  they keep track of what is dynamic and whats not
+    #  that makes them useful for db query validation or user input validation
+    # template_str = t"Hello, {input("Enter your name: ")} 👋 Welcome back!"
+    # food = "cheese"
+    # template = t"Tasty {food}!"
+    # for part in template:
+    #     if isinstance(part, str):
+    #         print("String part:", part)
+    #     else:
+    #         print("Interpolation part:", part.value)
+
+
+def split_strings():
+    example_string = "This is a long string with a number 2134"
+    print(f"> Example string: {example_string}")
+
+    first_four = example_string[:4]
+    print(f"> First four: {first_four}")
+
+    last_four = example_string[-4:]
+    print(f"> Last four: {last_four}")
+
+    without_first_four = example_string[4:]
+    print(f"> Without first four: {without_first_four}")
+
+    without_last_four = example_string[:-4]
+    print(f"> Without last four: {without_last_four}")
+
+    with_replaced_l = example_string.replace("l", "p")
+    print(f"> With replaced l: {with_replaced_l}")
+
+    # Must use ascii chars
+    with_multiple_removed = example_string.translate({97: None, 101: None, 105: None, 111: None, 117: None})
+    print(f"> Without vocals: {with_multiple_removed}")
+
+    a_to_o = str.maketrans("a", "o")
+    with_o_instead_of_a = example_string.translate(a_to_o)
+    print(f"> With o instead of a: {with_o_instead_of_a}")
+
+    no_a = str.maketrans("", "", "a")
+    without_a = example_string.translate(no_a)
+    print(f"> Without a: {without_a}")
+
+    split_at_half_first = example_string[:(len(example_string) // 2)]
+    split_at_half_second = example_string[example_string.__len__() // 2:]
+    print(f"Split at half: [first] {split_at_half_first} [second] {split_at_half_second}")
+
+    removed_the_second = example_string[:2] + example_string[3:]
+    print(f"Removed the second: {removed_the_second}")
+
+    begin_inclusive_not_end = example_string[1:2]
+    print(f"Inclusive test: {begin_inclusive_not_end}")
+
+
+def run():
+    template_strings()
+    split_strings()

src/modules/statistics.py

@@ -1,39 +0,0 @@
-from math import sqrt, pi, e
-
-def population_variance(difference_list, mean):
-	summatory = 0.0
-	for diff in difference_list:
-		summatory += (diff - mean) ** 2
-	return summatory / len(difference_list)
-
-def population_variance_inline(difference_list):
-	return sum((v - (sum(difference_list) / len(difference_list))) ** 2 for v in difference_list) / len(difference_list)
-
-def sample_variance(difference_list):
-	mean = sum(difference_list) / len(difference_list)
-	return sum((diff - mean) ** 2 for diff in difference_list) / (len(difference_list) - 1)
-
-def population_standard_deviation(difference_list):
-	return sqrt(population_variance_inline(difference_list))
-
-def sample_standard_deviation(difference_list):
-	return sqrt(sample_variance(difference_list))
-
-def standard_deviation(difference_list, is_sample):
-	return sample_standard_deviation(difference_list) if is_sample else population_standard_deviation(difference_list)
-
-# PDF generates the Normal Distribution (symetric arround the mean)
-def probability_density_function(x: float, mean: float, standard_deviation: float):
-	return (1 / (standard_deviation * sqrt(2 * pi))) * (e ** ((-1/2) * (x - (mean ** 2)) / standard_deviation))
-
-
-def test_statistics_module():
-	print("=== Statistics module ===")
-	differences = [ -6.571, -5.571, -1.571, 0.429, 2.429, 3.429, 7.429 ]
-	print("The population variance is", population_variance(differences, sum(differences) / len(differences)), population_variance_inline(differences))
-	print("The standard deviation is", standard_deviation(differences, False))
-	sample = differences.copy()
-	del sample[3]
-	del sample[1]
-	print("The sample variance for a population is", sample_variance(sample))
-	print("The standard deviation for a population is", standard_deviation(sample, True))

src/modules/strings.py

@@ -1,3 +0,0 @@
-def t_strings():
-	my_template = "This is a value: {test}"
-	print(my_template.format(test="another"))

tests/test_essentials.py

@@ -25,3 +25,17 @@ def test_find_missing():
 	result = find_missing(input)
 	expected = 4
 	assert result == expected
+
+def test_rain_watter():
+	input = [3,0,1,0,4,0,2]
+	expected = 10
+	result = trap_rain_water(input)
+	assert result == expected
+	input = [3,0,2,0,4]
+	expected = 7
+	result = trap_rain_water(input)
+	assert result == expected
+	input = [1,2,3,4]
+	expected = 0
+	result = trap_rain_water(input)
+	assert result == expected