convtools is a python library to declaratively define conversions for processing collections, doing complex aggregations and joins.
Project description
convtools is a python library to declaratively define conversions for processing collections, doing complex aggregations and joins.
Once a conversion is defined, it can be compiled into an ad hoc code OR be reused for building more complex conversions.
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What’s the workflow?
from convtools import conversion as c
define conversions
(optional) store them somewhere for further reuse
call gen_converter method to compile the conversion into a function, written with an ad hoc code
(optional) it’s totally fine to generate converters at runtime, for simple conversions it takes less than 0.1-0.2 milliseconds to get compiled.
Please, see simple examples of group by, aggregate and join conversions below.
from datetime import date, datetime
from decimal import Decimal
from convtools import conversion as c
def test_doc__index_intro():
# ======== #
# GROUP BY #
# ======== #
input_data = [
{"a": 5, "b": "foo"},
{"a": 10, "b": "foo"},
{"a": 10, "b": "bar"},
{"a": 10, "b": "bar"},
{"a": 20, "b": "bar"},
]
conv = (
c.group_by(c.item("b"))
.aggregate(
{
"b": c.item("b"),
"a_first": c.ReduceFuncs.First(c.item("a")),
"a_max": c.ReduceFuncs.Max(c.item("a")),
}
)
.gen_converter(debug=True)
)
assert conv(input_data) == [
{"b": "foo", "a_first": 5, "a_max": 10},
{"b": "bar", "a_first": 10, "a_max": 20},
]
# ========= #
# AGGREGATE #
# ========= #
conv = c.aggregate(
{
# list of "a" values where "b" equals to "bar"
"a": c.ReduceFuncs.Array(c.item("a")).filter(c.item("b") == "bar"),
# "b" value of a row where "a" has Max value
"b": c.ReduceFuncs.MaxRow(
c.item("a"),
).item("b", default=None),
}
).gen_converter(debug=True)
assert conv(input_data) == {"a": [10, 10, 20], "b": "bar"}
# ==== #
# JOIN #
# ==== #
collection_1 = [
{"id": 1, "name": "Nick"},
{"id": 2, "name": "Joash"},
{"id": 3, "name": "Bob"},
]
collection_2 = [
{"ID": "3", "age": 17, "country": "GB"},
{"ID": "2", "age": 21, "country": "US"},
{"ID": "1", "age": 18, "country": "CA"},
]
input_data = (collection_1, collection_2)
conv = (
c.join(
c.item(0),
c.item(1),
c.and_(
c.LEFT.item("id") == c.RIGHT.item("ID").as_type(int),
c.RIGHT.item("age") >= 18,
),
how="left",
)
.pipe(
c.list_comp(
{
"id": c.item(0, "id"),
"name": c.item(0, "name"),
"age": c.item(1, "age", default=None),
"country": c.item(1, "country", default=None),
}
)
)
.gen_converter(debug=True)
)
assert conv(input_data) == [
{"id": 1, "name": "Nick", "age": 18, "country": "CA"},
{"id": 2, "name": "Joash", "age": 21, "country": "US"},
{"id": 3, "name": "Bob", "age": None, "country": None},
]
Also there are more after the Installation section.
Why would you need this?
you believe that Python is awesome enough to have powerful aggregations and joins
you like the idea of having something else write an unpleasant ad hoc code for you
you need to serialize/deserialize objects
you need to define dynamic data transforms based on some input, which becomes available at runtime
you want to reuse field-wise transformations across the project without worrying about huge overhead of calling tens of functions per row/object, especially when there are thousands of them to be processed
Is it any different from tools like Pandas?
convtools doesn’t need to wrap data in any container to provide useful API, it just writes ad hoc python code under the hood
convtools is a lightweight library with no dependencies (however optional black is highly recommended for pretty-printing generated code when debugging)
convtools is about defining and reusing conversions – declarative approach, while wrapping data in high-performance containers is more of being imperative
Description
The speed of convtools comes from the approach of generating code & compiling conversion functions, which don’t have any generic code like superfluous loops, ifs, unnecessary function calls, etc.
So you can keep following the DRY principle by storing and reusing the code on the python expression level, but at the same time be able to run the gen_converter and get the compiled code which doesn’t care about being DRY and is generated to be highly specialized for the specific need.
There are group_by & aggregate conversions with many useful reducers:
from common Sum, Max
and less widely supported First/Last, Array/ArrayDistinct
to DictSum-like ones (for nested aggregation) and MaxRow/MinRow (for finding an object with max/min value and further processing)
There is a join conversion (inner, left, right, outer, cross are supported), which processes 2 iterables and returns a generator of joined pairs.
Thanks to pipes & labels it’s possible to define multiple pipelines of data processing, including branching and merging of them.
Tapping allows to add mutation steps not to rebuild objects from the scratch at every step.
- Every conversion:
contains the information of how to transform an input
can be piped into another conversion (same as wrapping)
can be labeled to be reused further in the conversions chain
has a method gen_converter returning a function compiled at runtime
despite being compiled at runtime, is debuggable with pdb due to linecache populating.
Installation:
pip install convtools
All-in-one example #1: deserialization & data preps
from datetime import date, datetime
from decimal import Decimal
from convtools import conversion as c
def test_doc__index_deserialization():
class Employee:
def __init__(self, **kwargs):
self.kwargs = kwargs
input_data = {
"objects": [
{
"id": 1,
"first_name": "john",
"last_name": "black",
"dob": None,
"salary": "1,000.00",
"department": "D1 ",
"date": "2000-01-01",
},
{
"id": 2,
"first_name": "bob",
"last_name": "wick",
"dob": "1900-01-01",
"salary": "1,001.00",
"department": "D3 ",
"date": "2000-01-01",
},
]
}
# get by "department" key and then call method "strip"
department = c.item("department").call_method("strip")
first_name = c.item("first_name").call_method("capitalize")
last_name = c.item("last_name").call_method("capitalize")
# call "format" method of a string and pass first & last names as parameters
full_name = c("{} {}").call_method("format", first_name, last_name)
date_of_birth = c.item("dob")
# partially initialized "strptime"
parse_date = c.call_func(
datetime.strptime, c.this(), "%Y-%m-%d"
).call_method("date")
conv = (
c.item("objects")
.pipe(
c.generator_comp(
{
"id": c.item("id"),
"first_name": first_name,
"last_name": last_name,
"full_name": full_name,
"date_of_birth": c.if_(
date_of_birth,
date_of_birth.pipe(parse_date),
None,
),
"salary": c.call_func(
Decimal,
c.item("salary").call_method("replace", ",", ""),
),
# pass a hardcoded dict and to get value by "department" key
"department_id": c.naive(
{
"D1": 10,
"D2": 11,
"D3": 12,
}
).item(department),
"date": c.item("date").pipe(parse_date),
}
)
)
.pipe(
c.dict_comp(
c.item("id"), # key
# write a python code expression, format with passed parameters
c.inline_expr("{employee_cls}(**{kwargs})").pass_args(
employee_cls=Employee,
kwargs=c.this(),
), # value
)
)
.gen_converter(debug=True)
)
result = conv(input_data)
assert result[1].kwargs == {
"date": date(2000, 1, 1),
"date_of_birth": None,
"department_id": 10,
"first_name": "John",
"full_name": "John Black",
"id": 1,
"last_name": "Black",
"salary": Decimal("1000.00"),
}
assert result[2].kwargs == {
"date": date(2000, 1, 1),
"date_of_birth": date(1900, 1, 1),
"department_id": 12,
"first_name": "Bob",
"full_name": "Bob Wick",
"id": 2,
"last_name": "Wick",
"salary": Decimal("1001.00"),
}
Under the hood the compiled code is as follows:
def converter_i5(data_):
global add_label_, get_by_label_
pipe_ua = data_["objects"]
pipe_ro = (
{
"id": i_j4["id"],
"first_name": i_j4["first_name"].capitalize(),
"last_name": i_j4["last_name"].capitalize(),
"full_name": "{} {}".format(
i_j4["first_name"].capitalize(), i_j4["last_name"].capitalize()
),
"date_of_birth": (
strptime_pa(i_j4["dob"], "%Y-%m-%d").date()
if i_j4["dob"]
else None
),
"salary": Decimal_sb(i_j4["salary"].replace(",", "")),
"department_id": v_o1[i_j4["department"].strip()],
"date": strptime_pa(i_j4["date"], "%Y-%m-%d").date(),
}
for i_j4 in pipe_ua
)
return {i_tj["id"]: (Employee_1y(**i_tj)) for i_tj in pipe_ro}
All-in-one example #2: word count
import re
from datetime import date, datetime
from decimal import Decimal
from itertools import chain
from convtools import conversion as c
def test_doc__index_word_count():
# Let's say we need to count words across all files
input_data = [
"war-and-peace-1.txt",
"war-and-peace-2.txt",
"war-and-peace-3.txt",
"war-and-peace-4.txt",
]
# # iterate an input and read file lines
#
# def read_file(filename):
# with open(filename) as f:
# for line in f:
# yield line
# extract_strings = c.generator_comp(c.call_func(read_file, c.this()))
# to simplify testing
extract_strings = c.generator_comp(
c.call_func(lambda filename: [filename], c.this())
)
# 1. make ``re`` pattern available to the code to be generated
# 2. call ``finditer`` method of the pattern and pass the string
# as an argument
# 3. pass the result to the next conversion
# 4. iterate results, call ``.group()`` method of each re.Match
# and call ``.lower()`` on each result
split_words = (
c.naive(re.compile(r"\w+"))
.call_method("finditer", c.this())
.pipe(
c.generator_comp(
c.this().call_method("group", 0).call_method("lower")
)
)
)
# ``extract_strings`` is the generator of strings
# so we iterate it and pass each item to ``split_words`` conversion
vectorized_split_words = c.generator_comp(c.this().pipe(split_words))
# flattening the result of ``vectorized_split_words``, which is
# a generator of generators of strings
flatten = c.call_func(
chain.from_iterable,
c.this(),
)
# aggregate the input, the result is a single dict
# words are keys, values are count of words
dict_word_to_count = c.aggregate(
c.ReduceFuncs.DictCount(c.this(), c.this(), default=dict)
)
# take top N words by:
# - call ``.items()`` method of the dict (the result of the aggregate)
# - pass the result to ``sorted``
# - take the slice, using input argument named ``top_n``
# - cast to a dict
take_top_n = (
c.this()
.call_method("items")
.pipe(sorted, key=lambda t: t[1], reverse=True)
.pipe(c.this()[: c.input_arg("top_n")])
.as_type(dict)
)
# the resulting pipeline is pretty self-descriptive, except the ``c.if_``
# part, which checks the condition (first argument),
# and returns the 2nd if True OR the 3rd (input data by default) otherwise
pipeline = (
extract_strings.pipe(flatten)
.pipe(vectorized_split_words)
.pipe(flatten)
.pipe(dict_word_to_count)
.pipe(
c.if_(
c.input_arg("top_n").is_not(None),
c.this().pipe(take_top_n),
)
)
# Define the resulting converter function signature.
# In fact this isn't necessary if you don't need to specify default values
).gen_converter(debug=True, signature="data_, top_n=None")
assert pipeline(input_data, top_n=3) == {"war": 4, "and": 4, "peace": 4}
Generated code:
def aggregate_1d(data_):
global add_label_, get_by_label_
_none = v_nn
agg_data_v0_ = _none
expected_checksum_ = 1
checksum_ = 0
it_ = iter(data_)
for row_ in it_:
if agg_data_v0_ is _none:
agg_data_v0_ = {row_: 1}
if agg_data_v0_ is not _none:
checksum_ |= 1
if checksum_ == expected_checksum_:
break
else:
if row_ not in agg_data_v0_:
agg_data_v0_[row_] = 1
else:
agg_data_v0_[row_] = agg_data_v0_[row_] + 1
for row_ in it_:
if row_ not in agg_data_v0_:
agg_data_v0_[row_] = 1
else:
agg_data_v0_[row_] = agg_data_v0_[row_] + 1
result_ = dict() if agg_data_v0_ is _none else agg_data_v0_
return result_
def converter_dd(data_, top_n=None):
global add_label_, get_by_label_
pipe_zb = (lambda_nf(i_oa) for i_oa in data_)
pipe_3m = from_iterable_ry(pipe_zb)
pipe_i2 = (
(i_bn.group(0).lower() for i_bn in v_rl.finditer(i_pu))
for i_pu in pipe_3m
)
pipe_4q = from_iterable_ry(pipe_i2)
pipe_v0 = aggregate_1d(pipe_4q)
return (
dict(
sorted(pipe_v0.items(), key=lambda_o1, reverse=True)[
(slice(None, top_n, None))
]
)
if (top_n is not None)
else pipe_v0
)
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