UnixJunkie
diff --git a/‎maths/series/arithmetic_mean.py‎
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+"""
+ARITHMETIC MEAN : https://en.wikipedia.org/wiki/Arithmetic_mean
+
+"""
+
+
+def is_arithmetic_series(series: list) -> bool:
+    """
+    checking whether the input series is arithmetic series or not
+
+    >>> is_arithmetic_series([2, 4, 6])
+    True
+    >>> is_arithmetic_series([3, 6, 12, 24])
+    False
+    >>> is_arithmetic_series([1, 2, 3])
+    True
+    """
+    if len(series) == 1:
+        return True
+    common_diff = series[1] - series[0]
+    for index in range(len(series) - 1):
+        if series[index + 1] - series[index] != common_diff:
+            return False
+    return True
+
+
+def arithmetic_mean(series: list) -> float:
+    """
+    return the arithmetic mean of series
+
+    >>> arithmetic_mean([2, 4, 6])
+    4.0
+    >>> arithmetic_mean([3, 6, 9, 12])
+    7.5
+    >>> arithmetic_mean(4)
+    Traceback (most recent call last):
+        ...
+    ValueError: Input series is not valid, valid series - [2, 4, 6]
+    >>> arithmetic_mean([4, 8, 1])
+    Traceback (most recent call last):
+        ...
+    ValueError: Input list is not an arithmetic series
+    >>> arithmetic_mean([1, 2, 3])
+    2.0
+    >>> arithmetic_mean([])
+    Traceback (most recent call last):
+        ...
+    ValueError: Input list must be a non empty list
+
+    """
+    if not isinstance(series, list):
+        raise ValueError("Input series is not valid, valid series - [2, 4, 6]")
+    if len(series) == 0:
+        raise ValueError("Input list must be a non empty list")
+    if not is_arithmetic_series(series):
+        raise ValueError("Input list is not an arithmetic series")
+    answer = 0
+    for val in series:
+        answer += val
+    return answer / len(series)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()