python numpy learning note Data Structure: ndarray Useful functions copy or in-place

import numpy as np

Data Structure:

  1. Series
  2. DataFramework:
    A 2-D labeled data structure with columns of potentially different types.

DataFramework

DF Information:

df.index

df.columns

ndarray

  1. n multi dimension array
  2. A generic multidimensional container for homogeneous data, so it should be same type.
  3. It will convert type into homogeneous type

Create

1.

data1 = [1,2,3,4]
arr = np.array(data1)
arr = np.array(data1, dtype=np.float64)

out: array([1,2,3,4])

  1. Use zeros or ones

    np.zeros(10)
    np.ones(11)

  2. Use arange

    np.arange(15)

  3. Use eye/ identity to create a Square N x N identity matrix

Operations

Vectorization

arr * arr
arr - arr

Useful functions

  • dtype

    data.dtype

  • ndim

    arr2.ndim

  • shape

  • asarray

copy or in-place

  1. If you want a copy of a slice of an ndarray instead of view, you will need to explicitly copy the array. Use arr[5:8].copy()