Python Basic Grammar Cheat-Sheet

Calculate

print(15/7)                # 나눗셈, 2
print(15//7)            # 몫, 2
print(15%7)                # 나머지, 1
print(2**3)                # 제곱근, 8

Variable Type

Type

• String
• Boolean
• Integer
• Float

v = 1
print(type(v))        # int

Tuple, Dictionary, Set

Tuple

수정이 안되는 엘리먼트 집합 자료형

# define
tuple = ()
tupleA = tuple()
tupleA = (1, 2)
tupleB = (3, 4)

print( tupleA(0) )        # 1, 인덱스 접근 가능

tupleA + tupleB            # (1, 2, 3, 4)
tupleA * 2                # (1, 2, 1, 2)


# use case
## switch x, y without temporary variable
x = 1, y = 2
x, y = y, x

## return two varible
function1(x, y)
  return x+y, x*y

## List to Tuple, Tuple to List
tupleA = tuple( [1,2,3] )

listA = list( (1,2,3) )

Dictionary

수정이 가능한 key, value 형태의 데이터 셋

dic = {}
dic = dic()
dic = {'key1': 'value1', 'key2', 'value2'}

# get
dic['key1']        # value1

# add or edit
dic['key3'] = 'value3'

# delete
del dic['key3']

# functions
dic.items()        # get tuple (key, value)
dic.keys()        # get key array
dic.values()    # get value array

Set

집합연산을 지원하는 순서와 중복이 없는 데이터 셋. 순서가 없기때문에 인덱스로 접근 불가

setA = {1, 2, 3}
setA = set()
setA = set(1)
setA = set(1, 2, 3)        # 한 개 이상일 경우 { } 사용해야 함

# use
## check contains
'apple' in setA            # false
1 in setA                # true


## operation
setA = {1, 2, 3}
setB = {3, 4}

setA & setB            # {3}, 교집합
setA | setB            # {1, 2, 3, 4}, 합집합
setA - setB            # {1, 2}, 차집합
setA ^ setB            # {1, 2, 4}, xor

## list의 중복 제거
list(set(listA))

input, print

name = input("type your input : ")                # kim
print(name)        # kim

print("Hello, ", name)                            # Hello, kim
print("Hello, {0}, {1}".format(name, "woo"))    # Hello, kim, woo
print("Hello, {1}, {0}".format(name, "woo"))    # Hello, woo, kim
print("Hello, {0}, {0}".format(name, "woo"))    # Hello, kim, kim


v = 0.126
print( format(v, ".2f") )        # 0.13
print( format(v, ".4f") )        # 0.1260
# %s : string, %c : character, %d : int, %f : float

String

str = """
Hello,
World!
"""
str = "Hello, World!"


len(str)                    # 13
str.count("l")                # 3
str.find("e")                # 1
str.replace("Hello", "Hi")    # Hi, World!
str[0]            # H
str[0:2]        # He
str[:2]            # He
str[0:-2]        # Hello, Wor
str.split(',')    # ["Hello", " World!"]


str = "   strip   "
str.strip()        # strip

Array

arr = [1, "a", 3.5]
print( arr[2] )                # 3.5
print( arr[-1] )            # 3.5
print( arr[1:3] )            # ["a", 3.5]
print( arr.append(3) )        # [1, "a", 3.5, 3]
print( arr.remove("a") )    # [1, 3.5, 3]

del arr[1]
print( arr )                # [1, 3]
arr.insert(1, 5)
print( arr )                # [1, 5, 3]

arr.sort()        
print( arr )    # [1, 3, 5]
arr.reverse()    
print( arr )    # [5, 3, 1]

For, While, If

#for
for element in ['a', 'b', 'c', 'd']:
  print(element)        # a, b, c, d

for element in range(3)        # or range(0:3)
  print(element)        # 0, 1, 2

# while
while true:
  print("Hello World")
  break;

# if elif else
if n == 1:
  print('n is 1')
elif n == 2:
  print('n is 2')
else:
  print('n is ', n)

Class

# define
class People():
  id = 0
  name = ""

  def hello(self, args2):
      print("arg1 : ", arg1)
      return "Hello, " + self.name