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Numerical Python Provides efficient storage and operations on dense data buffers, i.e., arrays. I ndarray is the fundamental object I Vectorized (no loop) operations on arrays I Broadcasting I File IO amd memory-mapped files In [1]: import numpy as np 2 / 17
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NumPy Array Element Types Arrays have elements of homogeneous data type In [2]: nums = [1, 2, 3.14] In [3]: nums Out[3]: [1, 2, 3.14] In [4]: np.array(nums) Out[4]: array([ 1. , 2. , 3.14]) In [5]: type(Out[4][0]) Out[5]: numpy.float64 I Notice that the values were converted to floats. You can specify an explicit element type with the dtype keyword argument: In [6]: np.array(nums, dtype=’int’) Out[6]: array([1, 2, 3]) 3 / 17
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Basic Array Creation Pass list to np.array() (nested lists create multi-dimensional arrays) In [9]: np.array([[1,2,3],[4,5,6]]) Out[9]: array([[1, 2, 3], [4, 5, 6]]) Create a one-dimensional array of zeros, dtype defaults to float : In [10]: np.zeros(4) Out[10]: array([ 0., 0., 0., 0.]) Create a multi-dimensional array of 1s with element type int . Note that first argument is a tuple of array dimensions. In [11]: np.ones((2, 3), dtype=int)
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