For each element, return the lowest index in the string where substring sub is found.
Calls str.find element-wise.
For each element, return the lowest index in the string where substring sub is found, such that sub is contained in the range [start, end].
| Parameters : | a : array_like of str or unicode sub : str or unicode start, end : int, optional 
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| Returns : | out : ndarray or int 
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See also