# NumPy library in Python – Set 1:

In this, we will see the Python library NumPy, which is a very useful array processing library in Data Science.

###### What exactly is NumPy?

It is a general purpose array processing package. Provides a multi dimensional array object and tools as well for working with the arrays.

It is a package that is fundamentally there for scientific computations. So, some of the important features are as follows:

• It is a powerful N- dimensional array object.
• It has sophisticate broadcasting functions.
• Consists of tools for integration of C/C++ and Fortran code.
• It also has linear algebra, Fourier transform, and random number capabilities.

Apart from the scientific uses, it can also be there as efficient multi-dimensional container of generic data.

We can define arbitrary data types using NumPy, which allows it to speedily and seamlessly integrate to a large variety of data bases.

###### Installation:
• In case we are using Mac and Linux we can install NumPy using the pip command:

pip install numpy

• In case of Windows, we need to download the pre-built windows installer for NumPy as it does not have any package manager.
1. Arrays in NumPy – Its main object is a homogenous multidimensional array.
• It is nothing but a table of elements(usually numbers), all of same type and index by tuple of positive integers.
• In the NumPy library dimensions are known as axes. Rank is the number of axes.
• Array class of NumPy is ndarray.
###### Example: 1. Creation of Array: We can create arrays in various ways in NumPy.
• We can create array from a regular Python list or tuple using the function array. So, the array type will be deduce from the sequential elements.
• Most of the time, the elements in an array are not known but its size is known. NumPy offers functions for creation of arrays with initial placeholder content. Example: np.zeroes, np.ones, np.full, etc.
• For creation of sequence of numbers, Numpy will provide a function which is analogous to the range which returns arrays instead of lists.
• arrange: It will return evenly space values within a specific interval. The step size is specific.
• linespace: It will return evenly space values within a specific interval. The step size is specific.
• Reshaping an array: Reshape method can be there to reshape an array. In order to reshape an array we need to see that the original size of the array remains the same.
• Flatten array: We can get copy of full array collapse into one dimension, using flatten method. It will accept order argument. Its default value is ‘C’ (row-major order). For column major order we use ‘F’.   1. ###### Array Indexing

Array indexing is important for analyzing and manipulating array object. NumPy provides several ways of array indexing.

• Slicing: The arrays in NumPy can be slice. Arrays are multi-dimensional, so, we need to specify a slice for each dimension of array.
• Integer array Indexing: In this the lists are for indexing for each dimension. To construct a new arbitrary method, a one on one mapping is done for corresponding elements.
• Boolean array Indexing: It is a method there for selecting elements from aaray which satisfy some conditions. 1. ###### Basic Operations:

NumPy provides a wide range of built-in arithmetic operations.

• Operations on single array: We use overload arithmetic operatorsin order to do element wise operations on an array to create another array. In the case of +=, *= -= operators, the array existing is modified.  • ###### Binary Operations:

The operations are apply on array elementwise and new array class is create. All basic arithmetic operators can be use here. The existing array is modified in case of +=, -= and = operators. • Universal functions(ufunc): Numpy provides us with the mathematical functions like sin, cos, exp, etc. The functions operate elementwise on array and produce an array as output. 1. Sorting array: We use sort method to sort NumPy arrays.  So, to learn more about numpy in python for data science, you can check this and this as well.

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