# math filter

Author:
itchyfingrs
Posted:
April 11, 2011
Language:
Python
Version:
1.2
Score:
2 (after 2 ratings)

A filter for general math operations.

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29``` ```from django.template import Node, Library import math register = Library() # taken from http://lybniz2.sourceforge.net/safeeval.html # make a list of safe functions math_safe_list = ['acos', 'asin', 'atan', 'atan2', 'ceil', 'cos', 'cosh', 'degrees', 'e', 'exp', 'fabs', 'floor', 'fmod', 'frexp', 'hypot', 'ldexp', 'log', 'log10', 'modf', 'pi', 'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh'] # use the list to filter the local namespace math_safe_dict = dict([(k, getattr(math, k)) for k in math_safe_list]) # add any needed builtins back in. math_safe_dict['abs'] = abs @register.filter('math') def math_(lopr, expr): """Evals a math expression and returns it's value. "\$1" is a placeholder. Insert "\$1" in the expression where the value is to be used. All math functions such as abs, sin, cos, floor are supported. Example, a. You will be redirected in {{ seconds|math:"\$1 / 60.0" }} minutes b. Square of {{ x }} is {{ x|math:"\$1 * \$1" }} c. Square root of {{ x }} is {{ x|math:"sqrt(\$1)" }} d. Given x = {{ x }}, (2 + x) * 6 = {{ x|math:"(2 + \$1) * 6" }} """ if lopr: return eval(expr.replace('\$1', str(lopr)), {"__builtins__": None}, math_safe_dict) return '' ```

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