[Enh]: Support Arithmetic and Logical `Expr` methods (like Polars)

[arv-anshul]

We would like to learn about your use case. For example, if this feature is needed to adopt Narwhals in an open source project, could you please enter the link to it below?

Currently, chaining arithmetic and logical operations in Narwhals requires wrapping expressions in parentheses to ensure the correct order of operations. In contrast, Polars supports method-based alternatives for operators such as .add(), .sub(), .and_(), .eq(), etc., on expressions. This leads to more readable and fluent code.

Please describe the purpose of the new feature or describe the problem to solve.

It would be highly beneficial for Narwhals to implement a similar API, allowing expressions to be chained cleanly using methods instead of infix operators.

Current behaviour

(nw.col("price") / nw.col("item_count")).round(2)
((nw.col("a") > 10) & (nw.col("b") < 5)) | (nw.col("c") == 100)

After feature implementation

nw.col("price").truediv("item_count").round(2)

nw.col("a").gt(10).and_(nw.col("b").lt(5)).or_(nw.col("c").eq(100))

nw.col("discount").eq(0).or_(nw.col("total").gt(100)).and_(nw.col("status").eq("valid"))

nw.col("score").sub("penalty").mul(1.5).ge(75)

Suggest a solution if possible.

No response

If you have tried alternatives, please describe them below.

These methods are present in Polars API.

Arithmetic Operations from Polars API

Method	Description
add	Method equivalent of addition operator expr + other
sub	Method equivalent of subtraction operator expr - other
mul	Method equivalent of multiplication operator expr * other
truediv	Method equivalent of float division operator expr / other
floordiv	Method equivalent of integer division operator expr // other
mod	Method equivalent of modulus operator expr % other
pow	Method equivalent of exponentiation operator expr ** exponent
neg	Method equivalent of unary minus operator -expr

Logical Operations from Polars API

Method	Description
and_	Method equivalent of bitwise "and" operator expr & other & ...
or_	Method equivalent of bitwise "or" operator `expr
eq	Method equivalent of equality operator expr == other
eq_missing	Method equivalent of equality operator expr == other where None == None
ne	Method equivalent of inequality operator expr != other
ne_missing	Method equivalent of equality operator expr != other where None == None
ge	Method equivalent of “greater than or equal” operator expr >= other
gt	Method equivalent of “greater than” operator expr > other
le	Method equivalent of “less than or equal” operator expr <= other
lt	Method equivalent of “less than” operator expr < other
not_	Negate a boolean expression
xor	Method equivalent of bitwise exclusive‑or operator expr ^ other

Additional information that may help us understand your needs.

Check polars.Expr docs.

[dangotbanned]

Appreciate the detail here, but closing as a duplicate of #2213 which has an open PR in #2900

You're more than welcome to present this over there 🙂

[arv-anshul]

Ohh sorry! I didn't saw it. I hope it will get resolve soon... 🙂