Guided Notes

Search, Sort & Filter

Finding values with where and searchsorted, sorting, boolean filtering, and set operations.

Searching with where()

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np.where(condition) returns the indexes where a condition is true:

arr = np.array([1, 2, 3, 4, 5, 4, 4]) np.where(arr == 4) → (array([3, 5, 6]),) np.where(arr % 2 == 0) → indexes of the even values

The result is a tuple with one array per dimension.

With three arguments, np.where chooses values element by element:

np.where(arr > 3, 'high', 'low')