[Python tutorial] 2. Basic, Variables, Module, User input

Basic grammer

Indentation

if 5 > 2:
  print("Five is greater than two!")
# Five is greater than two!

if 5 > 2:
 print("Five is greater than two!")
if 5 > 2:
        print("Five is greater than two!")

Comments

# This is a comment.
"""
This is a comment
written in
more than just one line
"""

Variables

• 문자 또는 _로 시작
• 숫자로 시작할 수 없음
• 알파벳, 숫자, _만 사용
• 대소문자 구분

Creating Variables

x = 5 # int
y = "Apple" # str
a, b, c = "Apple", "Banana", "Melon"
d = e = f = "Orange"
print(x)
print(y)

Casting, specify the data type of a variable

x = str(3)    # '3'
y = int(3)    # 3
z = float(3)  # 3.0

Single or Double Quotes

x = "Apple"
x = 'Apple' # same value

변수이름 작성법

• Camel Case: myVarName = "Apple"
• Pascal Case: MyVarName = "Apple"
• Snake Case: my_var_name = "Apple"

Unpack Collection

fruits = ["apple", "banana", "cherry"] # list
x, y, z = fruits # Unpack
# x = "apple", y = "banana", z = "cherry"

Output Variables: print()

x = "hello"
y = " world"
print(x) # hello
print(x, y) # hello world
print(x + y) # hello world

x = 5
y = 10
z = "Apple"
print(x + y) # 15
print(x + z) # error
print(x, z) # 5 Apple

Global & Local Variables

x = "Apple" # global variable

def myfunc():
    x = "Orange" # local variable
    print(x + " is delicious")

print(x) # Apple: Global variable
myfunc() # Orange is delicious: Local variable

Global Keyword

def myfunc():
  global x
  x = "Apple"
  print(x + " is delicious")

myfunc() # Apple is delicious
print(x) # Apple

Module

• Module: code library

Create a Module: .py

# mymodule.py

def greeting(name):
  print("Hello, " + name)

person1 = {
  "name": "John",
  "age": 36,
  "country": "Norway"
}

Use a Module

import mymodule

mymodule.greeting("Jonathan")

Variables in Module

import mymodule

a = mymodule.person1["age"]
print(a)

alias: as

import mymodule as mx

a = mx.person1["age"]
print(a)

Built-in Modules

import platform

x = platform.system()
print(x)

dir()

• list all defined names in module

x = dir(platform)
print(x)

Import From Module

from mymodule import person1

print (person1["age"])
# from으로 부른 모듈의 부분을 사용할 때는 모듈이름을 붙이지 않음

User Input

username = input("Enter username:")