Tokenizers, parsers and expression calculators in Python

This module is a part of the Pip.Services polyglot microservices toolkit. It provides syntax and lexical analyzers and expression calculator optimized for repeated calculations.

The module contains the following packages:

• Calculator - Expression calculator
• CSV - CSV tokenizer
• IO - input/output utility classes to support lexical analysis
• Mustache - Mustache templating engine
• Tokenizers - lexical analyzers to break incoming character streams into tokens
• Variants - dynamic objects that can hold any values and operators for them

Quick links:

• API Reference
• Change Log
• Get Help
• Contribute

Use

Install the Python package as

pip install pip-services3-expressions

The example below shows how to use expression calculator to dynamically calculate user-defined expressions.

from pip_services4_expressions.variants.Variant import Variant
from pip_services4_expressions.calculator.variables.Variable import Variable
from pip_services4_expressions.calculator.ExpressionCalculator import ExpressionCalculator
from pip_services4_expressions.calculator.variables.VariableCollection import VariableCollection

# ...

clalculator = ExpressionCalculator()

clalculator.expression = "A + b / (3 - Max(-123, 1)*2)"
vars = VariableCollection()
vars.add(Variable("A", Variant(1)))
vars.add(Variable("B", Variant(3)))

result = clalculator.evaluate_with_variables(vars)
print('The result of the expression is ' + result.as_string)
# ...

This is an example to process mustache templates.

mustache = MustacheTemplate()
mustache.template = "Hello, {{{NAME}}}{{#ESCLAMATION}}!{{/ESCLAMATION}}{{#unless ESCLAMATION}}.{{/unless}}"
result = mustache.evaluate_with_variables({ 'NAME': 'Mike', 'ESCLAMATION': True }) 
print("The result of template evaluation is '" + result + "'")

Develop

For development you shall install the following prerequisites:

• Python 3.7+
• Visual Studio Code or another IDE of your choice
• Docker

Install dependencies:

pip install -r requirements.txt

Run automated tests:

python test.py

Generate API documentation:

./docgen.ps1

Before committing changes run dockerized build and test as:

./build.ps1
./test.ps1
./clear.ps1

Contacts

The module is created and maintained by:

• Sergey Seroukhov
• Danil Prisiazhnyi