Chen Tang - Learning Python with Keen (Session 1)

My older son, Keen, is six years old now and he’s getting interested in coding. So I’m now working on a series of Jupyter notebooks that introduce him to Python.

Although I’m more of an R user, I feel Python is a better language to start for kids.

(Thanks to the reticulate package, I am able to write and run Python code within RStudio. Mad respect to whoever developed this package!)

library(reticulate)

Session 1: Python Basics

1. Numbers

1.1. Using Python as a calculator

1 + 5

538687445 + 3897886465

4436573910

6 - 3

30 - 8

1.2. Variables

The equals sign (“=”) means assignment, e.g., \(x = 1\) gives the value \(1\) to variable \(x\).

1 + 5

x = 1
y = 5

x + y

x = 3

x + y

z = x - y
z

-2

Your turn: - Create two variables: a and b. Assign 5 to a, and 10 to b - Calculate the sum of a and b, save it to a third variable called c - Calculate \(a \times b\) (hint: In Python, the multiplication sign is “*” [asterisk]) - Calculate \(a \div b\) (The division sign is “/” [forward slash])

a = 5
b = 10

c = a + b

a * b

a / b

0.5

Mini Project:

Calculate \(1 + 2 + ... + 10\).

Hint:

\[1 + 2 + ... + k = \frac{k \times (k + 1)}{2}\]

(Why?)

# step 1: determine k
k = 10

# step 2: write the equation
k * (k + 1) / 2

[1] 55

# defining a function to take any k value
def calc_sum(k):
   s = k * (k + 1) / 2 
   return s

calc_sum(k = 1_000_000)

500000500000.0

1.3 Strings

s1 = "hello"
s2 = "Keen"

print(s1)

hello

print(s2)

Keen

print(s1 + s2)

helloKeen

print(s1 + ", " + s2)

hello, Keen

print(s1 + ", " + s2 + "!")

hello, Keen!

print("H" + s1[1:5] + ", " + s2 + "!")

Hello, Keen!

a1 = "4"
b5 = "14"

a1 + b5

'414'

Project:

# tell me about you
name = "huijing"
age = 19

print("Hello, " + name + "! You are " + str(age) + " years old.")

Hello, huijing! You are 19 years old.

name

'huijing'

"H" + name[1:]

'Huijing'

1.4 Lists

fruits = ["apple", "banana", "peach"]
keen = [2, 4, 1]
mom = [0, 1, 3]

# how many bananas did Keen eat this week?
print("Keen ate " + str(keen[1]) + " bananas this week.")

Keen ate 4 bananas this week.

# How many peaches did mon eat this week?
print("Mom ate " + str(mom[2]) + " peaches this week.")

Mom ate 3 peaches this week.

# How many bananas were eaten in total?
print("In total, " + str(keen[1] + mom[1]) + " were eaten this week")

In total, 5 were eaten this week