Week 3.2 — Intro to Python

Learning the Basic Grammatical Rules for Python

Sorry that this week’s updates have been delayed. Oh, boy. Pfizer hit me quite badly. Anyways, here we are to finally embark on the land of Python. Today, we’ll be exploring the most basic grammatical rules for Python.

1. Variables and Basic Computations

a = 3     # insert 3 into a
b = a     # insert a into b
a = a + 1 # insert a+1 into a
num1 = a*b # insert a*b into the variable num1
num2 = 99 # insert 99 into the variable num2
# variable names can be freely imposed
# yet, it is better to be organized!

2-1. Informational — Strings and Numbers

name = 'bob' # In a variable, a string,
num = 12 # a number, 
is_number = True # and a "Boolean" can be inserted 
########
# so can Lists and Dictionaries as follows:

2-2. Informational — List (same as in Javascript)

a_list = []
a_list.append(1) # insert 1 into the list
a_list.append([2,3]) # insert [2,3] into the list 
# a_list = [1,[2,3]]
# a_list[0] = 1
# a_list[1] = [2,3]
# a_list[1][0] = 2

2-3. Informational — Dictionary (same as in Javascript)

a_dict = {}
a_dict = {'name':'bob','age':21}
a_dict['height'] = 178
# a_dict = {'name':'bob','age':21,'height':178}
# a_dict['name'] = 'bob'
# a_dict['age'] = 21
# a_dict['height'] = 178

2-4. Informational — Dictionary-List Combination

people = [{'name':'bob','age':20},{'name':'carry','age':38}]
# people[0]['name'] = 'bob'
# people[1]['name'] = 'carry'
person = {'name':'john','age':7
people.append(person)
# people = [{'name':'bob','age':20},{'name':'carry','age:38},  
  {'name':'john','age':7}]
# people[2]['name'] = 'john'

3-1. Functions — Math vs. Javascript vs. Python

# Mathematics:
f(x) = 2*x+3 
y = f(2)
y = 7  
# Javascript:
function f(x) {
  return 2*x+3 
}  
# Python:
def f(x):  
  return 2*x+3  
y = f(2) 
display(y) = 7

3-2. Functions — Application

def sum_all(a,b,c):  
  return a+b+c  
def mul(a,b):  
  return a*b  
result = sum_all(1,2,3) + mul(10,10)
display(result) = 106

4. Conditional (if/else) Statements

def oddeven(num): # define the function
  if num%2 == 0   # if the remainder of num when divided by 2 is 0
    return True   # return "True"
  else:           # if not
    return False  # return "False"
result = oddeven(20)
display(result) = True

Example:

def is_adult(age):
  if age > 20:
    print('Adult!')
  else:
    print('Child!')
is_adult(30) = "Adult!"

5. “For” Loops

fruits = [‘apple’, ‘ornage’, ‘banana’, ‘pineapple’]
for fruit in fruits:
  print(fruit)
# apple, orange, banana, and pineapple printed separately 

Application:

fruits = [‘apple’, ‘ornage’, 'orange', ‘banana’, ‘pineapple’]
count = 0
for fruit in fruits:
  if fruit == 'orange':
    count += 1
print(count)
# shows the number of oranges in the list

Advancement:

def count_fruits(target):
  count = 0
  for fruit in fruits:
    if fruit == target:
      count += 1
  return count
apple_count = count_fruits('apple')
print(apple_count) # number of apples
orange_count = count_fruits('orange')
print(orange_count) # number of oranges

Another example:

people = [{'name': 'bob', 'age': 20},           
          {'name': 'carry', 'age': 38},           
          {'name': 'john', 'age': 7},           
          {'name': 'smith', 'age': 17},           
          {'name': 'ben', 'age': 27}]
for person in people:
  print (person['name'], person['age'])
def get_age(myname):
  for person in people:
    if person['name'] == myname:
      return person['age']
    else:
      return 'n/a'
print(get_age('bob')) = 20
print(get_age('brian')) = n/a

Well, that’s about it. I think Python seems much more intuitive than Javascript! Hopefully, I’ll be able to apply these rules for data crawling next time. Yup. That is right. We’ll be covering the application of Python in data crawling in the next post, and it will be enjoyable! See you then.

Fin.