A package that calculates the result of a mathematical expression given as a string
Project description
Math Calculator
A package that calculates the result of a mathematical expression given as a string.
In its base form the calculator accepts
- operands
int
s andfloat
s
- operators
- unary
+-
, - binary
+-*/
and - parantheses
()
- unary
In the future
pip install math_calculator
Getting Started
Getting your first application running is super easy.
"""
A small CLI application that endlessly takes user input and evaluates it as a mathematical expression
"""
from math_calculator import calc
while True:
# this will raise a SyntaxError if the expression is syntactically incorrect
# normally you should always catch that Exception
expression = input(">>> ")
print(calc(expression))
Customization
Math Calculator is built to be customized by you. It internally uses the Python parser however, so it's abilities cannot be changed fundamentally. For example operator assoziativity or how parentheses work cannot be altered.
This package consists of two main modules .implicit
and .explicit
.implicit
Checks if the expression is a valid mathematical expression and then eval
s it. This makes it totally safe to use - even when exposed to potencially malicious users.
.implicit
example
We might want to extend the calculator to allow powers (**
is the corresponding operator). To do that we can reach into math_calculator.implicit
and add ast
operations to the valid operations
import ast
from math_calculator.implicit import calc, valid_ops
valid_ops.add(ast.Pow)
assert calc("4**3") == 4**3
You can not only change the valid operations but also the allowed operands. We could for example add complex
numbers
from math_calculator.implicit import calc, allowed_types
allowed_types.add(complex)
assert calc("3*5j") == 15j
.explicit
Explicitly evaluates the expression. This allows you to modify the semantics.
.explicit
example
In many other programming languages 5 ^ 4
is the same as 5*5*5*5 = 625
. In Python however, ^
is the bitwise xor operator and 5 ^ 4
evaluates to 1
. Now we will redefine ^
to mean the same as **
by reaching into the .explicit
module:
import ast
import operator
from math_calculator.explicit import calc, op_map
op_map[ast.BitXor] = operator.__pow__
assert calc("5^4") == 625
math_parser
exports .explicit.calc
by default.
Further customization
If you want to change the fundamental syntax or semantics, you can file an issue. Then I will try my best at weighing cost vs gain
. If I deem your feature request as "unworthy", that should not stop you from forking this project and extending it on your own. I am available for any questions you might have.
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