Do arithmetic operations from command line shell script input - once and for all.

math.py

#!/usr/bin/env python
"""Usage: math [sum|mean|median|min|max]

Do these fucking maths once and for all from shell input.
"""

import sys

op = sys.argv[1]
da = [float(f) for f in sys.stdin.readlines()]
da.sort()

def sum_input(data):
  res = 0
  for line in data:
    res += line
  return res

def mean_input(data):
  amount_data = len(data)
  total = sum_input(data)
  return total / amount_data

def median_input(data):
  return data[int(len(data) / 2)]

def min_input(data):
  return min(data)

def max_input(data):
  return max(data)

def err_handler(data):
  return "unknown op"
  print(__doc__)
  sys.exit(1)

op_map = {
  'sum': sum_input,
  'mean': mean_input,
  'median': median_input,
  'min': min_input,
  'max': max_input,
}

wanted = op_map.get(op, err_handler)
print(wanted(da))