Lesson 21 Num Py Python MiniCourse University of

Lesson objectives 1. Use the Num. Py package 2 Python Mini-Course: Lesson 21 6/11/09

What is Num. Py? Num. Py is the fundamental package needed for scientific computing

Num. Py documentation Official documentation http: //docs. scipy. org/doc/ The Num. Py book http:

The ndarray data structure Num. Py adds a new data structure to Python –

Array shape ndarrays are rectangular The shape of the array is a tuple of

Array item types Every ndarray is a homogeneous collection of exactly the same data-type

Example: creating an array import numpy a = array([[1, 2, 3], [4, 5, 6],

Indexing arrays Use a tuple to index multi- dimensional arrays Example: a[1, 2] 11

Slicing arrays is almost the same as slicing lists, except you can specify multiple

Examples: Slicing arrays a[1] a[1, : ] a[1, 1: ] a[: 1, 1: ]

Some ndarray methods ndarray. tolist () The contents of self as a nested list

Some Num. Py functions abs() add() binomial() cumprod() cumsum() floor() histogram() 15 Python Mini-Course:

Suggested exercise Complete the desc_stat_calc. py program 16 Python Mini-Course: Lesson 21 6/11/09

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Lesson 21 Num. Py Python Mini-Course University of Oklahoma Department of Psychology 1 Python Mini-Course: Lesson 21 6/11/09

Lesson objectives 1. Use the Num. Py package 2 Python Mini-Course: Lesson 21 6/11/09

What is Num. Py? Num. Py is the fundamental package needed for scientific computing with Python. It contains: a powerful N-dimensional array object basic linear algebra functions basic Fourier transforms sophisticated random number capabilities tools for integrating Fortran code tools for integrating C/C++ code 3 Python Mini-Course: Lesson 21 6/11/09

Num. Py documentation Official documentation http: //docs. scipy. org/doc/ The Num. Py book http: //www. tramy. us/numpybook. pdf Example list http: //www. scipy. org/Numpy_Example_L ist_With_Doc 4 Python Mini-Course: Lesson 21 6/11/09

The ndarray data structure Num. Py adds a new data structure to Python – the ndarray An N-dimensional array is a homogeneous collection of “items” indexed using N integers Defined by: 1. the shape of the array, and 2. the kind of item the array is composed of 5 Python Mini-Course: Lesson 21 6/11/09

Array shape ndarrays are rectangular The shape of the array is a tuple of N integers (one for each dimension) 6 Python Mini-Course: Lesson 21 6/11/09

Array item types Every ndarray is a homogeneous collection of exactly the same data-type every item takes up the same size block of memory each block of memory in the array is interpreted in exactly the same way 7 Python Mini-Course: Lesson 21 6/11/09

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Example: creating an array import numpy a = array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) a. shape a. dtype 10 Python Mini-Course: Lesson 21 6/11/09

Indexing arrays Use a tuple to index multi- dimensional arrays Example: a[1, 2] 11 Python Mini-Course: Lesson 21 6/11/09

Slicing arrays is almost the same as slicing lists, except you can specify multiple dimensions 12 Python Mini-Course: Lesson 21 6/11/09

Examples: Slicing arrays a[1] a[1, : ] a[1, 1: ] a[: 1, 1: ] 13 Python Mini-Course: Lesson 21 6/11/09

Some ndarray methods ndarray. tolist () The contents of self as a nested list ndarray. copy () Return a copy of the array ndarray. fill (scalar) Fill an array with the scalar value 14 Python Mini-Course: Lesson 21 6/11/09

Some Num. Py functions abs() add() binomial() cumprod() cumsum() floor() histogram() 15 Python Mini-Course: Lesson 21 min() max() multipy() polyfit() randint() shuffle() transpose() 6/11/09

Suggested exercise Complete the desc_stat_calc. py program 16 Python Mini-Course: Lesson 21 6/11/09