Extension of base Python list
that you can query. Queries are chainable and invertable with logical operators (& | ~
). Simple operations such as .where(...)
, to filter, .select(...)
to choose fields, and .aggregate(...)
to e.g. sum over a field are supported. .groupby(...)
can be also used to .count()
and .aggregate(...)
QueryList
s as well.
pip install pyquerylist
Documentation is available at http://markmuetz.github.io/pyquerylist/.
from dataclasses import dataclass
from pyquerylist import Query as Q, QueryList
@dataclass
class Book:
name: str
price_pence: int
category: str
def price(self):
return self.price_pence / 100
def vat_price(self):
return self.price() * 1.2
books = QueryList(
[
Book('Three crows', 500, 'fantasy'),
Book('Molly had a little calf', 200, 'child'),
Book('Time for another', 150, 'bargain'),
Book('Of stars and mud', 700, 'highbrow'),
Book('The Fruggalo', 300, 'child'),
Book('Three women in a canoe', 120, 'classic'),
Book('Who turns the page', 700, 'mystery'),
Book('The sword of silver', 300, 'fantasy'),
Book('Murder at 30000 ft', 150, 'mystery'),
Book('Once I saw a little mouse', 50, 'child'),
Book('The Leonardo code', 20, 'bargain'),
Book('The place we are at', 900, 'highbrow'),
]
)
if __name__ == '__main__':
print(books.count())
# books can be filtered on one of their fields.
print(books.where('name=="The Fruggalo"').count())
# This can also be done using a query.
print(books.where(Q('name=="The Fruggalo"')).count())
# Queries can be inverted.
print(books.where(~Q('name=="The Fruggalo"')).count())
# books is a list -- can be indexed or sliced:
print(books[:3])
# books can be filtered on multiple fields, showing price <= 3.
# if a field is a function (is callable) - it will be called (i.e. price).
print(books.where('(category=="fantasy")&(price<=3)'))
# Equivalent to above using combined queries.
print(books.where(Q('category=="fantasy"') & Q('price<=3')))
# These are equivalent, but not considered equal due to different definition.
print(Q(lambda x: x.price <= 5) != Q('price <= 5'))
# Queries can be combined using logical operators, and ordered by field(s).
print(
books.where(Q('category in ["fantasy", "mystery"]') | Q('price <= 3'))
.orderby('price', order='descending')
.select(fields=['category', 'price'])
)
# `lambda`s can be used, and fields can be chosen using `.select(...)`.
print(
books.where(Q('category == "fantasy"') | Q(lambda x: x.price() * 2 <= 6)).select(fields=['category', 'price'])
)
# Select can also take a function/lambda:
print(books.select(func=lambda b: b.price() * 2))
# Simple aggregate operations available.
print(books.aggregate(sum, 'price'))
print(books.aggregate(sum, ['price', 'vat_price']))
# Simple group by operator (returns a dict subclass), with group operations count and aggregate.
print(books.groupby('category')['mystery'])
print(books.groupby('category').count())
print(books.groupby('category').aggregate(sum, 'price'))
# QueryLists can be formatted for tabular display.
print(books.where('category=="fantasy"').tabulate(['name', 'price']))