Method: Polars::Functions#format

Defined in:
lib/polars/functions/as_datatype.rb

#format(f_string, *args) ⇒ Expr

Format expressions as a string.

Examples:

df = Polars::DataFrame.new(
  {
    "a": ["a", "b", "c"],
    "b": [1, 2, 3]
  }
)
df.select(
  [
    Polars.format("foo_{}_bar_{}", Polars.col("a"), "b").alias("fmt")
  ]
)
# =>
# shape: (3, 1)
# ┌─────────────┐
# │ fmt         │
# │ ---         │
# │ str         │
# ╞═════════════╡
# │ foo_a_bar_1 │
# │ foo_b_bar_2 │
# │ foo_c_bar_3 │
# └─────────────┘

Parameters:

  • f_string (String) —

    A string that with placeholders. For example: "hello_{}" or "{}_world

  • args (Object) —

    Expression(s) that fill the placeholders

Returns:



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# File 'lib/polars/functions/as_datatype.rb', line 582

def format(f_string, *args)
  if f_string.scan("{}").length != args.length
    raise ArgumentError, "number of placeholders should equal the number of arguments"
  end

  exprs = []

  arguments = args.each
  f_string.split(/(\{\})/).each do |s|
    if s == "{}"
      e = Utils.wrap_expr(Utils.parse_into_expression(arguments.next))
      exprs << e
    elsif s.length > 0
      exprs << lit(s)
    end
  end

  concat_str(exprs, separator: "")
end