# Session 1: Python Basics#

## 1.1. Using Python as a calculator#

1 + 5

6

538687445 + 3897886465

4436573910

6 - 3

3

30 - 8

22


## 1.2. Variables#

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

1 + 5

6

x = 1
y = 5

x + y

6

x = 3
x + y

8

z = x - y
z

-2


1. Create two variables: a and b. Assign 5 to a, and 10 to b

2. Calculate the sum of a and b, save it to a third variable called c

3. Calculate $$a \times b$$ (hint: In Python, the multiplication sign is “*” [asterisk])

4. Calculate $$a \div b$$ (The division sign is “/” [forward slash])

a = 5
b = 10

c = a + b
c

15

a * b

50

a / b

0.5


## Project#

Calculate $$1 + 2 +, ..., + k$$

Hint:

$\frac{k \times (k + 1)}{2}$
# step 1: determine k
k = 10

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

55.0

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!

a = 2
b = 3
s = "Hi"

a + b

5

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

"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) + " bananas this week.")

Keen ate 4 bananas this week.

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

Mom ate 3 peaches this week.

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

In total, 5 were eaten this week