Intro to Python

A Tour of Python with Real World Code

Created by jyn using reveal.js

Who's using Python?

Python in 5 minutes

Comparing Python to Java

Declarations


i = 1
d = 1.2
s = "hello, world"
l = [1, 2, 3]
                                

int i = 1;
double d = 1.2;
String s = "hello, world";
int[] i = {1, 2, 3};

Duck Typing


l = [1, 1.2, "hello, world"]
                                

List<Object> l = Arrays.asList(1, 1.2, "hello, world");

One slide on dictionaries

What's the difference?


d = {0: 'a', 1: 'b', 2: 'c'}
a = ['a', 'b', 'c']
print(d[0])  # prints 'a'
print(a[0])  # prints 'a'

Keys don't have to be integers


d = {'Monday': 'MATH 374', 'Tuesday': 'CSCE 146'}
print(d['Monday'])  # prints 'MATH 374'
Web query parameter example

What's GrepMe?

GroupMe doesn’t have a working search and it made me sad. So I wrote my own in Python!

Yes, I absolutely used this talk to advertise on of my side projects.

What does it look like?

  • Text highlighting
  • Searches in reverse chronological order
  • Can output dates
  • Can search by who liked a message
  • Can search multiple groups at a time

How does it work?

Let's look at the source code
Groupme API Reference

One slide on keyword arguments

What's this do?


def f(**kwargs):
  for key, value in kwargs.items():
    print(key, value)

f(a='b', c='d')  # prints 'a b\nc d'

Reference

Compares code in Python to code that does the same thing in Java

  1. printing to the console
  2. for-each loops
  3. generics
  4. doc-comments
  5. varargs
  6. lambdas

Printing to the console


print("Hello, world!")
                                

System.out.println("Hello, world!");

For-Each loops


  for i in [1, 2, 3]:
    print(i)
                                  

  for (int i : Arrays.asList(1, 2, 3)) {
    System.out.println(i);
  }

Generics

Python doesn't have generics, or rather, everything is generic! It uses duck-typing instead.


def makeList(element):
  return [element]
                                  

<T> List<T> makeList(T element) {
  ArrayList<T> myList = new ArrayList<T>();
  myList.add(element);
  return myList;
}

Documentation Comments


"""
This documents the function 'my_function'

Longer descriptions go here, in plain text
"""
def my_function():
  return 4  # guaranteed by IEEE to be random
                                

/**
 * This documents the function 'my_function'
 *
 * 
Longer descriptions go here, in HTML markup

 * @return A random integer between 0 and 1000
 */
int my_function() {
  return 4;
}

Variadic Arguments


def print(*args):
  for arg in args:
    print(arg)
                                

void print(Object ... args) {
  for (Object arg : args) {
    System.out.println(arg);
  }
}

First-Class and Anonymous Functions


def call_with_one(f):
  return f(1)

call_with_one(lambda arg: print(arg))
                                

void call_with_one(IntConsumer f) {
  f.accept(1);
}
call_with_one(i -> System.out.println(i));