This posts only use as a remainder
Variable
Multiple assignment
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| x, y, name, is_cool = (1, 2.5, 'a name', True)
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Casting
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| x = str(x)
# x will be string
y = int(y)
# y will be an integer
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String
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| name = 'Brad'
age = 37
print('name is' + name + ' and age is ' + str(age))
print('name is {name} and age is {age}'.format(name = name, age = age))
print(f'name is {name} and age is {age}')
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Methods
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| # Capitalize string
print(s.capitalize())
# Make all uppercase
print(s.upper())
# Make all lower
print(s.lower())
# Swap case
print(s.swapcase())
# Get length
print(len(s))
# Replace
print(s.replace('world', 'everyone'))
# Count
sub = 'h'
print(s.count(sub))
# Starts with
print(s.startswith('hello'))
# Ends with
print(s.endswith('d'))
# Split into a list
print(s.split())
# Find position
print(s.find('r'))
# Is all alphanumeric
print(s.isalnum())
# Is all alphabetic
print(s.isalpha())
# Is all numeric
print(s.isnumeric())
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List
A List is a collection which is ordered and changeable. Allows duplicate members.
Tuple
A Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
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| # Create tuple
fruits = ('Apples', 'Oranges', 'Grapes')
# Using a constructor
# fruits2 = tuple(('Apples', 'Oranges', 'Grapes'))
# Single value needs trailing comma
fruits2 = ('Apples',)
# Get value
print(fruits[1])
# Can't change value
# fruits[0] = 'Pears'
# Delete tuple
del fruits2
# Get length
print(len(fruits))
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set
A Set is a collection which is unordered and unindexed. No duplicate members.
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| # Create set
fruits_set = {'Apples', 'Oranges', 'Mango'}
# Check if in set
print('Apples' in fruits_set)
# Add to set
fruits_set.add('Grape')
# Remove from set
fruits_set.remove('Grape')
# Add duplicate
fruits_set.add('Apples')
# Clear set
fruits_set.clear()
# Delete not work
# del fruits_set
print(fruits_set)
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Dictionary
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| # Create dict
person = {
'first_name': 'John',
'last_name': 'Doe',
'age': 30
}
# Use constructor
# person2 = dict(first_name='Sara', last_name='Williams')
# Get value
print(person['first_name'])
print(person.get('last_name'))
# Add key/value
person['phone'] = '555-555-5555'
# Get dict keys
print(person.keys())
# Get dict items
print(person.items())
# Copy dict
person2 = person.copy()
person2['city'] = 'Boston'
# Remove item
del(person['age'])
person.pop('phone')
# Clear
person.clear()
# Get length
print(len(person2))
# List of dict
people = [
{'name': 'Martha', 'age': 30},
{'name': 'Kevin', 'age': 25}
]
print(people[1]['name'])
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Functions
A function is a block of code which only runs when it is called. In Python, we do not use curly brackets, we use indentation with tabs or spaces
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| def sayHello(name='Sam'):
print(f'Hello {name}')
# Return values
def getSum(num1, num2):
total = num1 + num2
return total
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lambda function
A lambda function is a small anonymous function.
A lambda function can take any number of arguments, but can only have one expression. Very similar to JS arrow functions
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| getSum2 = lambda num1, num2: num1 + num2
print(getSum(10, 3))
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conditionals
if elif else
Comparison Operators (==, !=, >, <, >=, <=) - Used to compare values
Logical operators (and, or, not) - Used to combine conditional statements
Membership Operators (not, not in) - Membership operators are used to test if a sequence is presented in an object
Identity Operators (is, is not) - Compare the objects, not if they are equal, but if they are actually the same object, with the same memory location:
Loop
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| people = ['John', 'Paul', 'Sara', 'Susan']
# Simple for loop
for person in people:
print(f'Current Person: {person}')
# Break
for person in people:
if person == 'Sara':
break
print(f'Current Person: {person}')
# Continue
for person in people:
if person == 'Sara':
continue
print(f'Current Person: {person}')
# range
for i in range(len(people)):
print(people[i])
for i in range(0, 11):
print(f'Number: {i}')
# While loops execute a set of statements as long as a condition is true.
count = 0
while count < 10:
print(f'Count: {count}')
count += 1
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Modules
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| # Core modules
import datetime
from datetime import date
import time
from time import time
# Pip module
# pip3 install camelcase
from camelcase import CamelCase
# Import custom module
import validator
from validator import validate_email
# today = datetime.date.today()
today = date.today()
# timestamp = time.time()
timestamp = time()
c = CamelCase()
# print(c.hump('hello there world'))
email = 'test#test.com'
if validate_email(email):
print('Email is valid')
else:
print('Email is bad')
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validator.py
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| import re
def validate_email(email):
if len(email) > 7:
return bool(re.match("^.+@(\[?)[a-zA-Z0-9-.]+.([a-zA-Z]{2,3}|[0-9]{1,3})(]?)$", email))
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Classes
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| # Create class
class User:
# Constructor
def __init__(self, name, email, age):
self.name = name
self.email = email
self.age = age
def greeting(self):
return f'My name is {self.name} and I am {self.age}'
def has_birthday(self):
self.age += 1
# Extend class
class Customer(User):
# Constructor
def __init__(self, name, email, age):
self.name = name
self.email = email
self.age = age
self.balance = 0
def set_balance(self, balance):
self.balance = balance
def greeting(self):
return f'My name is {self.name} and I am {self.age} and my balance is {self.balance}'
# Init user object
brad = User('Brad Traversy', 'brad@gmail.com', 37)
# Init customer object
janet = Customer('Janet Johnson', 'janet@yahoo.com', 25)
janet.has_birthday()
janet.set_balance(500)
print(janet.greeting())
brad.has_birthday()
print(brad.greeting())
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File
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| # Open a file
myFile = open('myfile.txt', 'w')
# Get some info
print('Name: ', myFile.name)
print('Is Closed : ', myFile.closed)
print('Opening Mode: ', myFile.mode)
# Write to file
myFile.write('I love Python')
myFile.write(' and JavaScript')
myFile.close()
## with as will automatic run close()
with open('myfile.txt', 'w') as myFile:
pass
# Append to file
myFile = open('myfile.txt', 'a')
myFile.write(' I also like PHP')
myFile.close()
# Read from file
myFile = open('myfile.txt', 'r+')
text = myFile.read(100)
print(text)
myFile.close()
## Read one line and read all line
myFile = open('myfile.txt', 'r+')
print(myFile.readline())
print(myFile.readlines())
myFile.close()
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Python & Json
JSON is commonly used with data APIS. Here how we can parse JSON into a Python dictionary
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| import json
# Sample JSON
userJSON = '{"first_name": "John", "last_name": "Doe", "age": 30}'
# Parse to dict
user = json.loads(userJSON)
# print(user)
# print(user['first_name'])
car = {'make': 'Ford', 'model': 'Mustang', 'year': 1970}
carJSON = json.dumps(car)
print(carJSON)
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