https://github.com/javascriptdude/whereval

Python Tool for parsing SQL like where expressions and evaluating against live data
https://github.com/javascriptdude/whereval

Last synced: 3 months ago
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Python Tool for parsing SQL like where expressions and evaluating against live data

• Host: GitHub
• URL: https://github.com/javascriptdude/whereval
• Owner: JavaScriptDude
• License: mit
• Created: 2022-04-09T05:59:05.000Z (almost 3 years ago)
• Default Branch: main
• Last Pushed: 2023-05-06T18:15:41.000Z (almost 2 years ago)
• Last Synced: 2024-10-12T21:19:12.007Z (4 months ago)
• Language: Python
• Size: 43 KB
• Stars: 2
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
## WherEval

Tool for parsing SQL like where expressions and evaluating against live data 

### Installation

```

python3 -m pip install whereval

```

### Inspiration

This tool will scratch an itch I've had for some cli tools where I want to pass complex filter expressions to control output / processing.

For instance with my `histstat` fork, I would like to have better filtering of networking information to be output to sqlite. See: https://github.com/JavaScriptDude/histstat

Another usecase for this is a tool I've wanted to write where I can write a `tail -f` wrapper in python where I can define a filter in cli parameters to limit output to the console. Have not written this yet but its on my todo now that I've got this API.

### API Example

#### (Ex1) Basic Concept:

```python3

from datetime import date

from whereval import Where, util as wutil

print("\n(Ex1) Basic Idea")

sw = wutil.StopWatch()

# Where query (terse example)

qry = "(f0>=2+f1=1+f2='s')|(f3~'foo%')"

# Field and type spec

spec = {'f0': int,'f1': bool,'f2': str,'f3': str, 'f4': dt_date}

# Instantiate Where

#  - Parses query and uses data to form rules for data types and fields

wher = Where(query=qry, spec=spec)

print(f"Query:\n . raw:\t{qry}\n . compiled: {wher}\n\nTests:")

def _print(wher, data, tup): 

	(ok, result, issues) = tup

	if not ok:

		print(f"Eval failed for {wher}. Issues: {issues}")

	else:

		print(f"\t{result}\tw/ data: {data}")

# Evaluate expression against real data

data = {'f0': 2, 'f1': True ,'f2': 's', 'f3': 'foobar'}

_print(wher, data, wher.evaluate(data))

# For different data

data['f3'] = 'bazbar'

_print(wher, data, wher.evaluate(data))

# For different data

data['f0'] = 1

_print(wher, data, wher.evaluate(data))

print(f"Completed. Elapsed: {sw.elapsed(3)}s")

```

#### Output of print:

```

(Ex1) Basic Idea

Query:

 . raw:	(f0>=2+f1=1+f2='s')|(f3~'foo%')

 . compiled: ( ( f0 >= 2 AND f1 = 1 AND f2 = 's' ) OR ( f3 like 'foo%' ) )

Tests:

	True	w/ data: {'f0': 2, 'f1': True, 'f2': 's', 'f3': 'foobar'}

	True	w/ data: {'f0': 2, 'f1': True, 'f2': 's', 'f3': 'bazbar'}

	False	w/ data: {'f0': 1, 'f1': True, 'f2': 's', 'f3': 'bazbar'}

Completed. Elapsed: 0.003s

```

### Query Syntax:

```

# General:

#  Query must begin with '(' and end with ')'

#  NOT, IN, BETWEEN must be followed by parenthesis '('

# Boolean Operators:

#   AND, OR, NOT

# Equality Operators:

#  =, !=, <, <=, >, >=, like

# Special:

#   !   -->  NOT

#   +   -->  AND

#   |   -->  OR

#   <>  -->  !=

#   ~   -->  like

```