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dicteval

Library to evaluate expressions in dict/json objects.

Requirements

  • Python 3.6+

Basic Usage

Module dicteval will evaluate basic types with no modifications but it will evaluate dicts (or json objects) containing keys started with = (equal) symbol as an expression:

>>> from dicteval import dicteval
>>> dicteval(3)
3
>>> dicteval([3, 5])
[3, 5]
>>> dicteval((5, 3))
[5, 3]
>>> dicteval({"=sum": [3, 5]})
8
>>> dicteval({"=": 5})  # = symbol alone is a 'nop' function
5

You can provide a dictionary with context to be used during evaluation process.

>>> dicteval({"=": "!{var}"}, context={"var": 1.0})
1.0

You can also wrap your string content with @{} to force a Python eval() with the context provided:

>>> dicteval({"=sum": [3, "@{var + 2}"]}, context={"var": 3})
8

Warning

This functionality will be removed (or changed) in future releases for security reasons.

Functions

You can use the following builtin functions in your expressions:

Function =any

Returns True if any element of sequence is true.

>>> dicteval({"=any": [1, 2, 3]})
True
>>> dicteval({"=any": [0, 0]})
False

Function =eq

Returns True if all elements of sequence are equals:

>>> dicteval({"=eq": [1, 1, 1, 1]})
True

Function =if

Evaluates condition and returns first value if true, otherwise, returns second value. If no false value is supplied, it is assumed to be None.

>>> dicteval({"=if": [{"=": "@{var > 5}"}, "yes", "no"]}, context={"var": 6})
'yes'
>>> dicteval({"=if": [{"=": "@{var > 5}"}, "yes", "no"]}, context={"var": 4})
'no'
>>> dicteval({"=if": [{"=": "@{var > 5}"}, "yes"]}, context={"var": 4})

Function =neq

Returns True if elements of sequence are different:

>>> dicteval({"=neq": [1, 1, 1, 5]})
True

Function = (or nop)

Returns the same values passed as arguments:

>>> dicteval({"=": [1, 2, 3, 4]})
[1, 2, 3, 4]
>>> dicteval({"=nop": "spam"})
'spam'

Function =not

Returns the boolean inverse of argument:

>>> dicteval({"=not": False})
True
>>> dicteval({"=not": True})
False
>>> dicteval({"=not": None})
True
>>> dicteval({"=not": "XYZ"})
False

Function =sum

Returns a number with the sum of arguments:

>>> dicteval({"=sum": [3, 5]})
8

Function =mul

Returns a number with the product of arguments:

>>> dicteval({"=mul": [3, 5]})
15

Function =all

Return True if all elements of the iterable are true (or if the iterable is empty)

>>> dicteval({"=all": (True, False)})
False
>>> dicteval({"=all": (True, True)})
True

Function =divmod

Returns a tuple containing the quotient and remainder after division:

>>> dicteval({"=divmod": [8,3]})
(2, 2)
>>> dicteval({"=divmod": [7.5,2.5]})
(3.0, 0.0)

Function =zip

Return list of aggregate tuples constructed from elements of multiple iterables.

>>> dicteval({"=zip": [[1, 2, 3], [4, 5], [6, 7, 8, 9]]})
[(1, 4, 6), (2, 5, 7)]

To Do

  • Add more functions to the builtin language

Contribute

To contribute to dicteval:

  1. Clone this repository and cd into it
  2. Install dev dependencies with [pipenv](https://github.com/pypa/pipenv) `bash pipenv install --dev `
  3. Create a branch, like git checkout -b [feature_name]
  4. Git commit changes
  5. Pull request

License

This software is licensed under MIT license.

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Evaluate expressions in dict/json objects

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