Pure-python command-line calculator

Calculate expression like python, with builtins and math module functions and constants. Support import of third-party functions and constants from modules

Python Programming Language Foundation Hometask

You are proposed to implement pure-python command-line calculator using python 3.6.

Requirements

Calculator should be a command-line utility which receives mathematical expression string as an argument and prints evaluated result:

$ pycalc '2+2*2'
6

It should provide the following interface:

$ pycalc --help
usage: pycalc [-h] [-m MODULE [MODULE ...]] EXPRESSION

Pure-python command-line calculator.

positional arguments:
  EXPRESSION            expression string to evaluate

optional arguments:
  -h, --help            show this help message and exit
  -m MODULE [MODULE ...], --use-modules MODULE [MODULE ...]
                        additional modules to use

In case of any mistakes in the expression utility should print human-readable error explanation with "ERROR: " prefix:

$ pycalc '15(25+1'
ERROR: brackets are not balanced
$ pycalc 'sin(-Pi/4)**1.5'
ERROR: negative number cannot be raised to a fractional power

Mathematical operations calculator must support

• arithmetic (+, -, *, /, //, %, ^) (^ is a power)
• comparison (<, <=, ==, !=, >=, >)
• built-in python functions (abs, pow, round)
• functions from standard python module math (trigonometry, logarithms, etc.)
• functions and constants from modules provided with --use-modules option

Non-functional requirements

• It is mandatory to use argparse module.
• Codebase must be covered with unittests with at least 70% coverage.
• Usage of eval and exec is prohibited.

Distribution

• Utility should be wrapped into distribution package with setuptools.
• This package should export CLI utility named pycalc.

Codestyle

• Docstrings are mandatory for all methods, classes, functions and modules.
• Code must correspond to pep8 (use pycodestyle utility for self-check).
  • You can set line length up to 120 symbols.

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Implementations will be checked with the latest cPython interpreter of 3.6 branch.