Question
Why do the following code samples:
np.array([[1, 2], [2, 3, 4]])
np.array([1.2, "abc"], dtype=float)
all give the following error?
ValueError: setting an array element with a sequence.
Answer
Possible reason 1: trying to create a jagged array
You may be creating an array from a list that isn't shaped like a multi- dimensional array:
numpy.array([[1, 2], [2, 3, 4]]) # wrong!
numpy.array([[1, 2], [2, [3, 4]]]) # wrong!
In these examples, the argument to numpy.array contains sequences of
different lengths. Those will yield this error message because the input list
is not shaped like a "box" that can be turned into a multidimensional array.
Possible reason 2: providing elements of incompatible types
For example, providing a string as an element in an array of type float:
numpy.array([1.2, "abc"], dtype=float) # wrong!
If you really want to have a NumPy array containing both strings and floats,
you could use the dtype object, which allows the array to hold arbitrary
Python objects:
numpy.array([1.2, "abc"], dtype=object)
