Comments (1)
I think this behavior comes from how polars adds constants to data frames.
Python's sum
has a starting value, which defaults to zero. The call sum([a, b])
runs as (0 + a) + b
.
When polars goes to add 0
to your first DataFrame
, it creates a Series
from the constant and infers an i64
type. Apparently, polars allows adding integers to dates, casting the date to an integer using the number of days since the epoch. When you add the second dataframe, addition doesn't crash because i64
+ date is allowed, even though date + date is not.
If you change the sum's starting value, you can get different types or different values:
>>> sum(
... [pl.DataFrame({'x':[1]}).cast({'x':pl.Date}), pl.DataFrame({'x':[2]}).cast({'x':pl.Date})],
... start=0.0,
... )
┌─────┐
│ x │
│ --- │
│ f64 │
╞═════╡
│ 3.0 │
└─────┘
>>> sum(
... [pl.DataFrame({'x':[1]}).cast({'x':pl.Date}), pl.DataFrame({'x':[2]}).cast({'x':pl.Date})],
... start=10,
... )
┌─────┐
│ x │
│ --- │
│ i64 │
╞═════╡
│ 13 │
└─────┘
The conversion of dates to integers is pretty weird:
>>> sum([pl.DataFrame({'x':[date(2024, 4, 1)]})])
┌───────┐
│ x │
│ --- │
│ i64 │
╞═══════╡
│ 19814 │
└───────┘
from polars.
Related Issues (20)
- Transpose option for `DataFrame.describe()` HOT 1
- Adding “Rounding half to even”
- `the name 'literal' is duplicate` when selecting a multi-element NumPy array or list
- Using pl.write_parquet() gives wrong results for values inside lists. HOT 12
- Concat of columns with lists of objects raises error HOT 3
- Append scalar column to list column HOT 2
- `pl.concat` inside `.agg()` raises InvalidOperationError - output length must be equal
- Make `int_range()` and `int_ranges()` work with no inputs and default to `int_range(0, pl.len())` HOT 7
- map_elements applied to dataframe with empty column or batch with empty column returns series with length 0. HOT 7
- `scan_csv`does not support a list of datatypes in `schema_overrides` HOT 1
- `read_csv` and `read_ipc` do not use native `storage_options` configuration keys
- DataFrame construction from numpy with dtype object HOT 2
- Arithmetic with nested arrays gives wrong results HOT 2
- Rename: Support for ignore_missing parameter HOT 1
- Cloud paths with square brackets in paths are not treated as non-glob paths, even with `glob=False`
- `.list.to_struct()` PanicException when used on non-list column
- `pl.col(col).last()` example shows both "max" and "last" behaviour HOT 1
- `any_horizontal` and `all_horizontal` treat null values differently than their vertical counterpart HOT 2
- Allow `os.PathLike` objects in `read_*` and `scan_*` functions HOT 1
- Improve error message for schema column mismatch.
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from polars.