jax-ml/jax · error · ValueError

the only valid string value of `right` is 'extrapolate', but

Error message

the only valid string value of `right` is 'extrapolate', but got: {right!r}

What it means

jnp.interp accepts the special string 'extrapolate' for the right argument (to extrapolate above the last xp point). Any other string is rejected; only 'extrapolate' or a numeric bound is valid.

Source

Thrown at jax/_src/numpy/lax_numpy.py:2615

           right: ArrayLike | str | None = None,
           period: ArrayLike | None = None) -> Array:
  x, xp, fp = util.ensure_arraylike("interp", x, xp, fp)
  if np.shape(xp) != np.shape(fp) or np.ndim(xp) != 1:
    raise ValueError("xp and fp must be one-dimensional arrays of equal size")
  x_arr, xp_arr = util.promote_dtypes_inexact(x, xp)
  fp_arr, = util.promote_dtypes_inexact(fp)
  del x, xp, fp

  if isinstance(left, str):
    if left != 'extrapolate':
      raise ValueError("the only valid string value of `left` is "
                       f"'extrapolate', but got: {left!r}")
    extrapolate_left = True
  else:
    extrapolate_left = False
  if isinstance(right, str):
    if right != 'extrapolate':
      raise ValueError("the only valid string value of `right` is "
                       f"'extrapolate', but got: {right!r}")
    extrapolate_right = True
  else:
    extrapolate_right = False

  if dtypes.issubdtype(x_arr.dtype, np.complexfloating):
    raise ValueError("jnp.interp: complex x values not supported.")

  if period is not None:
    if np.ndim(period) != 0:
      raise ValueError(f"period must be a scalar; got {period}")
    period = ufuncs.abs(period)
    x_arr = x_arr % period
    xp_arr = xp_arr % period
    xp_arr, fp_arr = lax.sort_key_val(xp_arr, fp_arr)
    xp_arr = concatenate([xp_arr[-1:] - period, xp_arr, xp_arr[:1] + period])
    fp_arr = concatenate([fp_arr[-1:], fp_arr, fp_arr[:1]])

View on GitHub (pinned to 1e1c6a8fc0)

Solutions

1. Use right='extrapolate' or a numeric scalar
2. Fix string typos
3. Leave right unset for the default fp[-1] behavior

Example fix

// before
jnp.interp(x, xp, fp, right='extrapolte')
// after
jnp.interp(x, xp, fp, right='extrapolate')

if isinstance(right, str) and right != 'extrapolate':
    right = 'extrapolate'  # or raise

def is_valid_interp_bound(v) -> bool:
    return not isinstance(v, str) or v == 'extrapolate'

catch ValueError, fall back to numeric bound or default

When it happens

Trigger: Calling jnp.interp(x, xp, fp, right='extend') or any non-'extrapolate' string for right.

Common situations: Migrating SciPy np.interp-style code with custom sentinel strings; copy-paste from codebases that use different extrapolation flags.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• the only valid string value of `left` is 'extrapolate', but
• Unknown resize method "{s}"
• Use 'cuda', 'rocm', or 'oneapi' for lax.platform_dependent.
• 'trans' value must be 0, 1, or 2, got {trans}
• Got unexpected `to` value. Allowed `to` values are: {_allowe

AI-assisted analysis of jax-ml/jax@1e1c6a8fc0 (2026-08-27). Data as JSON: /api/errors/906dd8130d215d87. Report an issue: GitHub.