Lesson List

Welcome to AI Programming with Python

Start using AI techniques and developing skills related to programming, linear algebra, and neural networks.

Why Python Programming

Start coding with Python, drawing upon libraries and automation scripts to solve complex problems quickly.

Data Types and Operators

Control Flow

Functions

Scripting

Lab Classifying Images

In this project, learners will be testing their newly-acquired Python coding skills by using a trained image classifier. They will need to use the trained neural network to classify images of dogs (by breeds) and compare the output with the known dog breed classification. Learners will have a chance to build their own functions, use command line arguments, test the runtime of the code, create a dictionary of lists, and more.

NumPy

Learn how to use all the key tools for working with data in Python: Jupyter Notebooks, NumPy, Anaconda, Pandas, and Matplotlib.

Pandas

Matplotlib and Seaborn Part 1

Learn how to use Matplotlib to choose appropriate plots for one and two variables based on the types of data you have.

Matplotlib and Seaborn Part 2

Introduction

Learn the foundational math needed for AI success—vectors, linear transformations, and matrices—as well as the linear algebra behind neural networks.

Vectors

Linear Combination

Linear Transformation and Matrices

Vectors Lab

Linear Combination Lab

Linear Mapping Lab

Linear Algebra in Neural Networks

Introduction to Neural Networks

Gain a solid foundation in the latest trends in AI: neural networks, deep learning, and PyTorch.

Implementing Gradient Descent

Training Neural Networks

Deep Learning with PyTorch

Create Your Own Image Classifier

How Do I Continue From Here

Go to course home
13. Strings

In the video above, at the 1:32 mark, the str is written as follows salesman = '"I think you're an encyclopedia salesman'", but the closing string literals should be double quotes " followed by single quotes '.

 

Strings

Strings in Python are shown as the variable type str. You can define a string with either double quotes " or single quotes '. If the string you are creating actually has one of these two values in it, then you need to be careful to assure your code doesn’t give an error.

>>> my_string = 'this is a string!'
>>> my_string2 = "this is also a string!!!"

You can also include a  in your string to be able to include one of these quotes:

>>> this_string = 'Simon's skateboard is in the garage.'
>>> print(this_string)
Simon's skateboard is in the garage.

If we don’t use this, notice we get the following error:

>>> this_string = 'Simon's skateboard is in the garage.'
  File "<ipython-input-20-e80562c2a290>", line 1
    this_string = 'Simon's skateboard is in the garage.'
                         ^
SyntaxError: invalid syntax

The color highlighting is also an indication of the error you have in your string in this second case. There are a number of other operations you can use with strings as well. In this video you saw a few:

>>> first_word = 'Hello'
>>> second_word = 'There'
>>> print(first_word + second_word)

HelloThere

>>> print(first_word + ' ' + second_word)

Hello There

>>> print(first_word * 5)

HelloHelloHelloHelloHello

>>> print(len(first_word))

5

Unlike the other data types you have seen so far, you can also index into strings, but you will see more on this soon! For now, here is a small example. Notice Python uses 0 indexing – we will discuss this later in this lesson in detail.

>>> first_word[0]

H

>>> first_word[1]

e
 

The len() function

len() is a built-in Python function that returns the length of an object, like a string. The length of a string is the number of characters in the string. This will always be an integer.

There is an example above, but here’s another one:

print(len("ababa") / len("ab"))
2.5

You know what the data types are for len(“ababa”) and len(“ab”). Notice the data type of their resulting quotient here.

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