normal python max function doesn't work and the error message is not helpful

[arnabanimesh]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

from datetime import datetime
import polars as pl

out_df = pl.read_csv(b"total_time,qty,end_time\n2009,106,2009")
out_df = out_df.select(pl.col("qty"),(pl.lit(datetime(2024,1,1,0,0,0),pl.Datetime)+pl.duration(minutes=max(0,pl.col("end_time").cast(pl.Int64)-pl.col("total_time").cast(pl.Int64)))).dt.strftime("%d-%m-%Y %H:%M").alias("start_time"))
print(out_df)

Using pl.max_horizontal instead of max works. But this should also work in a similar manner.

Log output

file < 128 rows, no statistics determined
no. of chunks: 1 processed by: 1 threads.
Traceback (most recent call last):
  File "D:\coding\postproc.py", line 7, in <module>
    out_df = out_df.select(pl.col("qty"),(pl.lit(datetime(2024,1,1,0,0,0),pl.Datetime)+pl.duration(minutes=max(0,pl.col("end_time").cast(pl.Int64)-pl.col("total_time").cast(pl.Int64)))).dt.strftime("%d-%m-%Y %H:%M").alias("start_time"))
                                                                                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Arnab\scoop\apps\python311\current\Lib\site-packages\polars\expr\expr.py", line 149, in __bool__
    raise TypeError(msg)
TypeError: the truth value of an Expr is ambiguous

Hint: use '&' or '|' to logically combine Expr, not 'and'/'or', and use `x.is_in([y,z])` instead of `x in [y,z]` to check membership.

Issue description

Error is being generated

Expected behavior

No error, normal output as per code

Installed versions

--------Version info---------
Polars:               0.20.6
Index type:           UInt32
Platform:             Windows-10-10.0.22631-SP0
Python:               3.11.7 (tags/v3.11.7:fa7a6f2, Dec  4 2023, 19:24:49) [MSC v.1937 64 bit (AMD64)]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          3.0.0
connectorx:           <not installed>
deltalake:            <not installed>
fsspec:               2023.12.2
gevent:               <not installed>
hvplot:               <not installed>
matplotlib:           3.8.2
numpy:                1.26.2
openpyxl:             3.1.2
pandas:               2.1.4
pyarrow:              14.0.2
pydantic:             <not installed>
pyiceberg:            <not installed>
pyxlsb:               1.0.10
sqlalchemy:           <not installed>
xlsx2csv:             0.8.2
xlsxwriter:           3.1.9

[Wainberg]

Here's a minimal example:

>>> max(pl.col.a, pl.col.b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "polars/expr/expr.py", line 148, in __bool__
    raise TypeError(msg)
TypeError: the truth value of an Expr is ambiguous

Hint: use '&' or '|' to logically combine Expr, not 'and'/'or', and use `x.is_in([y,z])` instead of `x in [y,z]` to check membership.

I agree that it would be nice to make max an alias for max_horizontal here, and similarly for min, all and any.

[arnabanimesh]

I think max is already kind of an alias of max_horizontal as my code outputs properly if you remove the qty column from the select statement in my code. This kind of inconsistent behaviour is unexpected.

[alexander-beedie]

You can't use the Python max function with a Polars expression ;)
You need to use Polars' own max or max_horizontal here.

max(0, pl.col("end_time"))
# TypeError: the truth value of an Expr is ambiguous

pl.max_horizontal(0, pl.col("end_time"))
# <polars.expr.expr.Expr at 0x29de1fc10>

[arnabanimesh]

At least change the error message. It is not helpful at all.