Method: Polars::StringExpr#extract_groups

Defined in:
lib/polars/string_expr.rb

#extract_groups(pattern) ⇒ Expr

Extract all capture groups for the given regex pattern.

Examples:

df = Polars::DataFrame.new(
  {
    "url": [
      "http://vote.com/ballon_dor?candidate=messi&ref=python",
      "http://vote.com/ballon_dor?candidate=weghorst&ref=polars",
      "http://vote.com/ballon_dor?error=404&ref=rust"
    ]
  }
)
pattern = /candidate=(?<candidate>\w+)&ref=(?<ref>\w+)/.to_s
df.select(captures: Polars.col("url").str.extract_groups(pattern)).unnest(
  "captures"
)
# =>
# shape: (3, 2)
# ┌───────────┬────────┐
# │ candidate ┆ ref    │
# │ ---       ┆ ---    │
# │ str       ┆ str    │
# ╞═══════════╪════════╡
# │ messi     ┆ python │
# │ weghorst  ┆ polars │
# │ null      ┆ null   │
# └───────────┴────────┘

Unnamed groups have their numerical position converted to a string:

pattern = /candidate=(\w+)&ref=(\w+)/.to_s
(
  df.with_columns(
    captures: Polars.col("url").str.extract_groups(pattern)
  ).with_columns(name: Polars.col("captures").struct["1"].str.to_uppercase)
)
# =>
# shape: (3, 3)
# ┌─────────────────────────────────┬───────────────────────┬──────────┐
# │ url                             ┆ captures              ┆ name     │
# │ ---                             ┆ ---                   ┆ ---      │
# │ str                             ┆ struct[2]             ┆ str      │
# ╞═════════════════════════════════╪═══════════════════════╪══════════╡
# │ http://vote.com/ballon_dor?can… ┆ {"messi","python"}    ┆ MESSI    │
# │ http://vote.com/ballon_dor?can… ┆ {"weghorst","polars"} ┆ WEGHORST │
# │ http://vote.com/ballon_dor?err… ┆ {null,null}           ┆ null     │
# └─────────────────────────────────┴───────────────────────┴──────────┘

Parameters:

  • pattern (String) —

    A valid regular expression pattern containing at least one capture group, compatible with the regex crate.

Returns:



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# File 'lib/polars/string_expr.rb', line 1190

def extract_groups(pattern)
  Utils.wrap_expr(_rbexpr.str_extract_groups(pattern))
end