# groups_have_uniform_coeffs

### groups_have_uniform_coeffs(op, , atol=1e-08, abs=True)

Returns, for each group, whether all of its coefficients are numerically equal.

With `abs` (the default), the coefficient *magnitudes* are compared, which is the assumption
that [`group_coeff_means()`](qiskit_fermions.operators.terms.group_coeff_means.html.md#qiskit_fermions.operators.terms.group_coeff_means) makes when it averages `abs(coeff)`. Without it, the
coefficients must match exactly. Note that a Hermitian group may legitimately fail the stricter
form, since a conjugate pair with complex coefficients has equal magnitudes but unequal
coefficients. If the operator tracks no groups, this returns `None`.

An empty or single-term group is trivially uniform.

#### NOTE
This is *not* a weaker form of [`groups_are_hermitian()`](qiskit_fermions.operators.terms.groups_are_hermitian.html.md#qiskit_fermions.operators.terms.groups_are_hermitian): neither implies the other.
Uniform coefficients do not make a group Hermitian, and a Hermitian group can mix
magnitudes.

```pycon
>>> from qiskit_fermions.operators import FermionOperator
>>> from qiskit_fermions.operators.terms.grouping import groups_have_uniform_coeffs
>>> op = FermionOperator.from_dict(
...     {
...         ((True, 0), (False, 1)): 1.0j,
...         ((True, 1), (False, 0)): -1.0j,
...     }
... )
>>> op.groups = [0, 0]
>>> groups_have_uniform_coeffs(op)  # equal magnitudes
[True]
>>> groups_have_uniform_coeffs(op, abs=False)  # but not equal coefficients
[False]
```

* **Parameters:**
  * **op** – the operator whose groups to check.
  * **atol** – The numerical accuracy upto which coefficients are considered equal. This value
    defaults to `1e-8`.
  * **abs** – Whether to compare coefficient magnitudes rather than the coefficients themselves. This
    value defaults to `True`.
* **Returns:**
  One flag per group index, or `None` if the operator tracks no groups.
* **Raises:**
  [**TypeError**](https://docs.python.org/3/builtins/exceptions.html#TypeError) – if `op` is not a supported operator type (see
      [`OperatorTrait`](qiskit_fermions.operators.OperatorTrait.html.md#qiskit_fermions.operators.OperatorTrait)).