typeddfs 0.5.0

Pandas DataFrame subclasses that enforce structure and can self-organize.

Typed DataFrames

Pandas DataFrame subclasses that enforce structure and can self-organize. Because your functions can’t exactly accept any DataFrame.

The subclassed DataFrames can have required and/or optional columns and indices, and support custom requirements. Columns are automatically turned into indices, which means read_csv and to_csv are always inverses. MyDf.read_csv(mydf.to_csv()) is just mydf.

The DataFrames will display nicely in Jupyter notebooks, and a few convenience methods are added, such as sort_natural and drop_cols. See the docs for more information.

pip install typeddfs[hdf5] to install.

Please note that HDF5 via pytables is unsupported in Python 3.9 on Windows as of 2021-02-03.

Simple example for a CSV like this:

key	value	note
abc	123	?

from typeddfs import TypedDfs

# Build me a Key-Value-Note class!
KeyValue = (
    TypedDfs.typed("KeyValue")        # typed means enforced requirements
    .require("key", dtype=str, index=True)  # automagically make this an index
    .require("value")                 # required
    .reserve("note")                  # permitted but not required
    .strict()                         # don’t allow other columns
).build()

# This will self-organize and use "key" as the index:
df = KeyValue.read_csv("example.csv")

# For fun, let"s write it and read it back:
df.to_csv("remke.csv")
df = KeyValue("remake.csv")
print(df.index_names(), df.column_names())  # ["key"], ["value", "note"]

# And now, we can type a function to require a KeyValue,
# and let it raise an `InvalidDfError` (here, a `MissingColumnError`):
def my_special_function(df: KeyValue) -> float:
    return KeyValue(df)["value"].sum()

All of the normal DataFrame methods are available. Use .untyped() or .vanilla() to make a detyped copy that doesn’t enforce requirements.

A small note of caution: natsort is no longer pinned to a specific major version as of version 0.5 because it receives somewhat frequent major updates. This means that the result of typed-df’s sort_natural could change. You can pin natsort to a specific major version; e.g. natsort = "^7" with Poetry.

Typed-Dfs is licensed under the Apache License, version 2.0. New issues and pull requests are welcome. Please refer to the contributing guide.
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