Functions

These functions are available from the polars module root and can be used as expressions, and sometimes also in eager contexts.

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Available in module namespace:

all([name])	Do one of two things.
any(name)	Evaluate columnwise or elementwise with a bitwise OR operation.
apply(exprs, function[, return_dtype, ...])	Apply a custom/user-defined function (UDF) in a GroupBy context.
arange()	Create a range expression (or Series).
arg_sort_by(exprs, *[, descending])	Return the row indices that would sort the columns.
avg()	Alias for mean.
coalesce(exprs, *more_exprs)	Folds the columns from left to right, keeping the first non-null value.
concat_list(exprs, *more_exprs)	Horizontally concatenate columns into a single list column.
concat_str(exprs, *[, separator])	Horizontally concatenate columns into a single string column.
corr(a, b, *[, method, ddof, propagate_nans])	Compute the pearson's or spearman rank correlation correlation between two columns.
count()	Count the number of values in this column/context.
cov(a, b)	Compute the covariance between two columns/ expressions.
cumfold(acc, function, exprs, *[, include_init])	Cumulatively accumulate over multiple columns horizontally/ row wise with a left fold.
cumreduce(function, exprs)	Cumulatively accumulate over multiple columns horizontally/ row wise with a left fold.
cumsum()	Cumulatively sum values in a column/Series, or horizontally across list of columns/expressions.
date(year, month, day)	Create a Polars literal expression of type Date.
datetime(year, month, day[, hour, minute, ...])	Create a Polars literal expression of type Datetime.
duration(*[, days, seconds, nanoseconds, ...])	Create polars Duration from distinct time components.
element()	Alias for an element being evaluated in an eval expression.
exclude(columns, *more_columns)	Represent all columns except for the given columns.
first()	Get the first value.
fold(acc, function, exprs)	Accumulate over multiple columns horizontally/ row wise with a left fold.
format(fstring, *args)	Format expressions as a string.
from_epoch()	Utility function that parses an epoch timestamp (or Unix time) to Polars Date(time).
groups(column)	Syntactic sugar for pl.col("foo").agg_groups().
head()	Get the first n rows.
list(name)	Aggregate to list.
lit(value[, dtype, allow_object])	Return an expression representing a literal value.
map(exprs, function[, return_dtype])	Map a custom function over multiple columns/expressions.
max()	Get the maximum value.
mean()	Get the mean value.
median()	Get the median value.
min()	Get the minimum value.
n_unique()	Count unique values.
pearson_corr(a, b[, ddof])	Compute the pearson's correlation between two columns.
quantile(column, quantile[, interpolation])	Syntactic sugar for pl.col("foo").quantile(..).
reduce(function, exprs)	Accumulate over multiple columns horizontally/ row wise with a left fold.
repeat()	Repeat a single value n times.
select([exprs])	Run polars expressions without a context.
spearman_rank_corr(a, b[, ddof, propagate_nans])	Compute the spearman rank correlation between two columns.
std()	Get the standard deviation.
struct()	Collect columns into a struct column.
sum()	Sum values in a column/Series, or horizontally across list of columns/expressions.
tail()	Get the last n rows.
var()	Get the variance.
when(expr)	Start a "when, then, otherwise" expression.

Available in expression namespace:

Expr.all()	Check if all boolean values in a Boolean column are True.
Expr.any()	Check if any boolean value in a Boolean column is True.
Expr.apply(function[, return_dtype, ...])	Apply a custom/user-defined function (UDF) in a GroupBy or Projection context.
Expr.count()	Count the number of values in this expression.
Expr.cumsum([reverse])	Get an array with the cumulative sum computed at every element.
Expr.exclude(columns, *more_columns)	Exclude columns from a multi-column expression.
Expr.first()	Get the first value.
Expr.head([n])	Get the first n rows.
Expr.list()	Aggregate to list.
Expr.map(function[, return_dtype, agg_list])	Apply a custom python function to a Series or sequence of Series.
Expr.max()	Get maximum value.
Expr.mean()	Get mean value.
Expr.median()	Get median value using linear interpolation.
Expr.min()	Get minimum value.
Expr.n_unique()	Count unique values.
Expr.quantile(quantile[, interpolation])	Get quantile value.
Expr.std([ddof])	Get standard deviation.
Expr.sum()	Get sum value.
Expr.tail([n])	Get the last n rows.
Expr.var([ddof])	Get variance.