1 A Taste of Python

Welcome to the world of Python.

Python is very simple language to learn, yet it is quite powerful.

Let’s get a taste of Python by looking at a couple of examples.

1.1 Python is Simple

Python is a very simple programming language and it is quite easy to learn.

Writing a hello-world program just takes a single line of code.

print("hello, world!")

hello, world!

It is very handy to use Python as a calculator.

print(1 + 2)

1.2 Python is Dynamically Typed

Python is a dynamically typed programming language, so you don’t need to declare type of variables.

x = 1
y = 2
print(x + y)

It is perfectly fine to reassign a variable to a value of a different type.

x = 1
print(x)

x = "foo"
print(x)

1
foo

While the variables do not have types associated with them, the values do have types. Python is strict about them and it doesn’t allow operations on incompatible datatypes.

1 + "2"

TypeError: unsupported operand type(s) for +: 'int' and 'str'

People often assume that a dynamically-typed language is also weekly-typed, which is the case for languages like Perl, PHP and even Javascript. Python is dynamically-typed, but also strongly-typed.

1.3 Python uses Indentation

Python uses indentation to identify the code that is part of a block.

marks = 50

if marks > 35:
    print("pass")
else:
    print("fail")

pass

Notice that Python doesn’t use the usual { and } characters to identify code blocks. It just uses indentation to identify the block of code that is part of compound statements like if, else, etc.

Here is another example:

numbers = [1, 2, 3, 4]

for n in numbers:
    print(n)
print("done")

1
2
3
4
done

1.4 Python is Expressive

Python has elegant data strucutres and many built-in functions.

Using them the right way leads to very elegant code.

For example, the following example computes the sum of squares of all even numbers below one million.

# sum of squares of all even numbers below one million
sum([n*n for n in range(1000000) if n % 2 == 0])

166666166667000000

Isn’t that almost like restating the problem?

Not impressed yet? Here is another gem to find the longest word in the english dictionary¹.

# what is the lonest word in the dictioanary
max(open("/usr/share/dict/words"), key=len)

"electroencephalograph's\n"

1.5 Python is Productive

Python has an extensive standard library and many third-party libraries.

The following example find the most popular repositories on github.

import requests

url = "https://api.github.com/search/repositories"
params = {
    "q": "language:python"
}

data = requests.get(url, params=params).json()

for repo in data['items'][:10]:
    print(repo['full_name'])

floodsung/Deep-Learning-Papers-Reading-Roadmap
microsoft/TaskMatrix
shadowsocks/shadowsocks
PaddlePaddle/PaddleOCR
fxsjy/jieba
streamlit/streamlit
tatsu-lab/stanford_alpaca
OpenBB-finance/OpenBBTerminal
luong-komorebi/Awesome-Linux-Software
AtsushiSakai/PythonRobotics

On unix machines, the words in the dictionary are usually available in the file /usr/share/dict/words.↩︎