Method: Polars::StringExpr#starts_with

Defined in:
lib/polars/string_expr.rb

#starts_with(prefix) ⇒ Expr

Check if string values start with a substring.

Examples:

df = Polars::DataFrame.new({"fruits" => ["apple", "mango", nil]})
df.with_columns(
  Polars.col("fruits").str.starts_with("app").alias("has_prefix")
)
# =>
# shape: (3, 2)
# ┌────────┬────────────┐
# │ fruits ┆ has_prefix │
# │ ---    ┆ ---        │
# │ str    ┆ bool       │
# ╞════════╪════════════╡
# │ apple  ┆ true       │
# │ mango  ┆ false      │
# │ null   ┆ null       │
# └────────┴────────────┘

Using starts_with as a filter condition:

df.filter(Polars.col("fruits").str.starts_with("app"))
# =>
# shape: (1, 1)
# ┌────────┐
# │ fruits │
# │ ---    │
# │ str    │
# ╞════════╡
# │ apple  │
# └────────┘

Parameters:

  • prefix (String) —

    Prefix substring.

Returns:



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# File 'lib/polars/string_expr.rb', line 927

def starts_with(prefix)
  prefix_rbexpr = Utils.parse_into_expression(prefix, str_as_lit: true)
  Utils.wrap_expr(_rbexpr.str_starts_with(prefix_rbexpr))
end