# filterlib
A filter library for python by Fabian Becker.
## What for?
With a `Filter` object you can easily check for attributes of an object to equal a given value.
## Usage
### How to create a filter
#### Create a filter using __init__()
Both attributes are optional.
`operator: str = "AND"` (`"AND"` or `"OR"`) sets the logical operator for the filter (checks all or any attributes).
`allow_missing_attributes: bool = False` sets the tolerance for missing attributes. If set to true it will skip if the attribute is missing in the object to check.
#### Create a filter from its representation
The return value of a filters `__repr__` attribute can be used to store and later on recreate a filter using `filter_from_repr`
```python
from filterlib import Filter, filter_from_repr
f = Filter()
print(f == filter_from_repr(repr(f)))
# f and filter_from_repr(f.__repr__()) is the same
```
#### Additional attributes
The attribute a filter checks for are variable
```python
from filterlib import Filter
# Use the following systax:
f = Filter(<Optional[attibute name]><attributes magic method>=<value>)
# For example:
f = Filter(a__eq__=1)
# You can also use multiple attributes:
f = Filter(b__lte__=5,
c__gt__=2)
# Or check for objects themselves
Filter(__eq__="Hello World!") == "Hello World!"
```
### Use a filter
Make sure you use the filters `__eq__` attribute.
```python
# Make sure you use
Filter() == x
# instead of
x == Filter()
```
## Example
```python
from filterlib import Filter
from typing import Optional
class Person:
def __init__(self,
name: str,
age: int,
best_friend: Optional[Person] = None):
self.name = name
self.age = age
self.best_fiend = best_friend
f = Filter(name__eq__="John")
p = Person(name="John", age=35)
print(f == p)
# True
f = Filter(name__ne__="John")
p = Person(name="John", age=35)
print(f == p)
# False
f = Filter(name__eq__="John", age__lte=40)
p = Person(name="John", age=35)
print(f == p)
# True
f = Filter(name__eq__="John", age__lte=20)
p = Person(name="John", age=35)
print(f == p)
# False
f = Filter(operator="OR",
name__eq__="John",
age__lte=20)
p = Person(name="John", age=35)
print(f == p)
# True
p = Person(name="John",
age=35,
best_friend=Person(name="Thomas",
age=36))
f = Filter(best_friend__name__eq__="Thomas",
age__lte=40)
print(f == p)
# True
```
## SQL compatability
You can use filters for sql statements
```python
from filterlib import Filter
import sqlite3
db = sqlite3.connect("myDB.sqlite")
db.execute("CREATE TABLE users(id, name)")
f = Filter(id__eq__=1)
db.execute(f"SELECT name FROM users WHERE {f}")
```
