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
19. String Methods

String Methods

In this video you were introduced to methods. Methods are like some of the functions you have already seen:

  1. len(“this”)
  2. type(12)
  3. print(“Hello world”)

These three above are functions – notice they use parentheses, and accept one or more arguments. Functions will be studied in much more detail in a later lesson!

A method in Python behaves similarly to a function. Methods actually are functions that are called using dot notation. For example, lower() is a string method that can be used like this, on a string called “sample string”: sample_string.lower().

Methods are specific to the data type for a particular variable. So there are some built-in methods that are available for all strings, different methods that are available for all integers, etc.

Below is an image that shows some methods that are possible with any string.

Each of these methods accepts the string itself as the first argument of the method. However, they also could receive additional arguments, that are passed inside the parentheses. Let’s look at the output for a few examples.

>>> my_string.islower()
True
>>> my_string.count('a')
2
>>> my_string.find('a')
3

You can see that the count and find methods both take another argument. However, the .islower() method does not accept another argument.

No professional has all the methods memorized, which is why understanding how to use documentation and find answers is so important. Gaining a strong grasp of the foundations of programming will allow you to use those foundations to use documentation to build so much more than someone who tries to memorize all the built-in methods in Python.

One important string method: format()

We will be using the format() string method a good bit in our future work in Python, and you will find it very valuable in your coding, especially with your print statements.

We can best illustrate how to use format() by looking at some examples:

# Example 1
print("Mohammed has {} balloons".format(27))
Mohammed has 27 balloons
# Example 2
animal = "dog"
action = "bite"
print("Does your {} {}?".format(animal, action))
Does your dog bite?
# Example 3
maria_string = "Maria loves {} and {}"
print(maria_string.format("math","statistics"))
Maria loves math and statistics

Notice how in each example, the number of pairs of curly braces {} you use inside the string is the same as the number of replacements you want to make using the values inside format().

More advanced students can learn more about the formal syntax for using the format() string method here.

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