R, Python 분석과 프로그래밍의 친구 (by R Friend)

 (1) 조건이 1개 일 때 if, else 분기문 (if, else branch statement with 1 condition)

# (1) if, else statement

print('Put your Python test score : ')

py_score = int(input())

if py_score >= 80:

    print('Your Python score is {0}'.format(py_score))

    print('Congratulations! You passed Python test. :-)')

else:

    print('Your Python score is {0}'.format(py_score))

    print('You failed Python test. Study more! T_T')

Put your Python test score :

90

Your Python score is 90

Congratulations! You passed Python test. :-)

Put your Python test score :

70

Your Python score is 70

You failed Python test. Study more! T_T

In [3]: print('Put your Python test score : ')

    ...:

    ...: py_score = int(input())

    ...:

    ...: if py_score >= 80 # Oops! Syntax Error due to no colon(:)

    ...:

    ...: print('Your Python score is {0}'.format(py_score))

    ...: print('Congratulations! You passed Python test. :-)')

    ...:

    ...:

    ...: else:

    ...:

    ...: print('Your Python score is {0}'.format(py_score))

    ...: print('You failed Python test. Study more! T_T')

    ...:

File "<ipython-input-18-b2c00ee4ee98>", line 5

if py_score >= 80 # Oops! Syntax Error due to no colon(:)

^

SyntaxError: invalid syntax

 (2) 조건이 2개 일 때 if, elif, else 분기문 

      (if, elif, else branch statement with multiple condition expressions)

# (2) if, elif, else statement

print('Put your Python test score : ')

py_score = int(input())

if py_score >= 80 and py_score <= 100:

    print('Your Python score is {0}'.format(py_score))

    print('Congratulations! You passed Python test')

elif py_score >= 0 and py_score < 80:

    print('Your Python score is {0}'.format(py_score))

    print('You failed Python test. Study more!')

else:

    print('You put the wrong score.')

Put your Python test score : 

150

You put the wrong score.

Put your Python test score : 

90

Your Python score is 90

Congratulations! You passed Python test

Put your Python test score : 

60

Your Python score is 60

You failed Python test. Study more!

Put your Python test score : 

-50

You put the wrong score.

 (3) if 조건문 안에 if 조건문을 중첩해서 프로그래밍 하기 (nested if statements)

# (3) nested if statements

print('Put your Python test score : ')

py_score = int(input())

if py_score <= 100:

    if py_score >= 80:       

        print('Your Python score is {0}'.format(py_score))

        print('Congratulations! You passed Python test. :-)')

    else:       

        if py_score < 80:

            if py_score > 0:

                print('Your Python score is {0}'.format(py_score))

                print('You failed Python test. Study more! T_T')

            else:                

                print('You put the wrong score.')

else:    

    print('You put the wrong score.')

Put your Python test score : 

150

You put the wrong score.

Put your Python test score : 

90

Your Python score is 90

Congratulations! You passed Python test. :-)

Put your Python test score : 

60

Your Python score is 60

You failed Python test. Study more! T_T

Put your Python test score : 

-50

You put the wrong score.

In [1]: a = 2 > 1

In [2]: a

Out[2]: True

In [3]: b = 2 < 1

In [4]: b

Out[4]: False

In [5]: type(a)

Out[5]: bool

 (1) 조건문에서의 참, 거짓 (True, False in Conditional statements)

# (1-1) Boolean False, True

In [6]: bool(False) # False

Out[6]: False

In [7]: bool(True) # True

Out[7]: True

# (1-2) None is False

In [8]: bool(None) # False

Out[8]: False

# (1-3) Number 0, 0.00 is False

In [9]: bool(0) # False

Out[9]: False

In [10]: bool(0.00) # False

Out[10]: False

In [11]: bool(5) # True

Out[11]: True

# (1-4) blank List [] is False

In [12]: bool([]) # False

Out[12]: False

In [13]: bool(['a', 'b']) # True

Out[13]: True

# (1-5) blank Tuple () is False

In [14]: bool(()) # False

Out[14]: False

In [15]: bool(('a', 'b')) # True

Out[15]: True

# (1-6) blank Dictionary {} is False

In [16]: bool({}) # False

Out[16]: False

In [17]: bool({'a': 'b'}) # True

Out[17]: True

  (2) 논리 연산자에서 참, 거짓 (True, False in Logical operators) : not, and, or

# (2-1) 피연산자 부정 'not' logical operator

In [18]: not True # False

Out[18]: False

In [19]: not False # True

Out[19]: True

In [20]: not 0 # True

Out[20]: True

In [21]: not 5 # False

Out[21]: False

In [22]: not None # True

Out[22]: True

In [23]: not '' # denial of blank String -> True

Out[23]: True

In [24]: not [] # denial of blank List -> True

Out[24]: True

In [25]: not () # denial of blank Tuple -> True

Out[25]: True

In [26]: not {} # denial of blank Dictionary -> True

Out[26]: True

In [27]: not 'ab' # False

Out[27]: False

In [28]: not ['a', 'b'] # False

Out[28]: False

In [29]: not ('a', 'b') # False

Out[29]: False

In [30]: not {'a' : 'b'} # False

Out[30]: False

In [31]: True and True # True

Out[31]: True

In [32]: True and False # False

Out[32]: False

In [33]: False and True # False

Out[33]: False

In [34]: False and False # False

Out[34]: False

In [35]: True or True # True

Out[35]: True

In [36]: True or False # True

Out[36]: True

In [37]: False or False # False

Out[37]: False

  (3) 비교 연산자에서의 참, 거짓 (True, False in Comparison operators) : ==, !=, >, >=, <, <=

# (3) Comparison(Relational) operators

In [39]: a = 1; b = 2; c = 2 # input data

# (3-1) == : If the values of two operands are equal, then the condition becomes true

In [40]: a == b # False

Out[40]: False

In [41]: b == c # True

Out[41]: True

In [42]: a != b # True

Out[42]: True

In [43]: b != c # False

Out[43]: False

In [39]: a = 1; b = 2; c = 2 # input data

# (3-3) > : If the value of left operand is greater than the value of right operand, 

# then condition becomes true

In [44]: a > b # False

Out[44]: False

In [45]: b > a # True

Out[45]: True

In [46]: b > c # False

Out[46]: False

In [39]: a = 1; b = 2; c = 2 # input data

# (3-4) >= : If the value of left operand is greater than or equal to the value of right operand, 

# then condition becomes true

In [47]: a >= b # False

Out[47]: False

In [48]: b >= a # True

Out[48]: True

In [49]: b >= c # True

Out[49]: True

In [39]: a = 1; b = 2; c = 2 # input data

# (3-5) < : If the value of left operand is less than the value of right operand, 

# then condition becomes true

In [50]: a < b # True

Out[50]: True

In [51]: b < a # False

Out[51]: False

In [52]: b < c # False

Out[52]: False

In [39]: a = 1; b = 2; c = 2 # input data

In [53]: a <= b # True

Out[53]: True

In [54]: b <= a # False

Out[54]: False

In [55]: b <= c # True

Out[55]: True

 1-1. len(dict): 사전의 총 길이 (total length of Dictionary)

# 1-1. len(dict) : Gives the total length of the dictionary

>>> dict_1 = {'name' : 'R Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> dict_1

{'name': 'R Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

>>> len(dict_1)

4

 1-2. str(dict): 사전을 문자열로 반환 (string representation of a Dictionary)

# 1-2. str(dict) : Produces a printable string representation of a dictionary

>>> str(dict_1)

"{'name': 'R Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}"

 1-3. type(variable): 입력 변수의 유형 반환 (returns the type of the passed variable)

# 1-3. type() : Returns the type of the passed variable

>>> type(dict_1)

<class 'dict'>

 2-1. dict.keys(): 사전의 키 목록

# 2-1. dict.keys(): Returns a list of all the available keys in the dictionary

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

...           'key3' : (1, 2, 3)}

>>> 

>>> dict_2

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

>>> dict_2.keys()

dict_keys(['key1', 'key2', 'key3'])

 2-2. dict.values(): 사전의 값 목록

# 2-2. dict.values(): Returns a list of all the values available in the dictionary

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

...           'key3' : (1, 2, 3)}

>>> 

>>> dict_2

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

>>> dict_2.values()

dict_values([123, 'abc', (1, 2, 3)])

 2-3. dict.items(): 사전의 (키, 값) 튜플 목록 

# 2-3. dict.items(): Returns a list of dict's (key, value) tuple pairs

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

...           'key3' : (1, 2, 3)}

>>> 

>>> dict_2

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

>>> dict_2.items()

dict_items([('key1', 123), ('key2', 'abc'), ('key3', (1, 2, 3))])

 2-4. dict.clear(): 사전의 모든 {키, 값} 셋 제거

# 2-4. dict.clear() : Removes all items from the dictionary

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

...           'key3' : (1, 2, 3)}

>>> 

>>> dict_2

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

>>> dict_2.clear()

>>> dict_2

{}

 2-5. dict.copy(): 사전의 {키 : 값} 셋 복사

# 2-5. dict.copy(): Returns a copy of the dictionary

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

...           'key3' : (1, 2, 3)}

>>> 

dict_2

>>> {'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

>>> dict_3 = dict_2.copy()

>>> dict_3

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

 2-6. dict.fromkeys(seq, value): seq, value 셋으로 신규 사전 생성

# 2-6. dict.fromkeys(): Creates a new dictionary with keys from seq and values set to value

>>> seq = ('key1', 'key2', 'key3')

>>> 

>>> dict_4 = dict.fromkeys(seq)

>>> dict_4

{'key1': None, 'key2': None, 'key3': None}

>>> 

>>> dict_4 = dict.fromkeys(seq, 123)

>>> dict_4

{'key1': 123, 'key2': 123, 'key3': 123}

2-7. dict.get(key, default=None): 키에 할당된 값 반환

# 2-7. dict.get(key, default=None): Returns a value for the given key

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

          'key3' : (1, 2, 3)}

... >>> 

>>> dict_2

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

>>> dict_2.get('key1', 'No_Key')

123

>>> dict_2.get('key5', 'No_Key') # If key is not available then returns 'No_Key'

'No_Key'

>>> dict_2.get('key5') # If key is not available then returns default value None

2-8. dict.setdefault(key, default=None) : 키에 할당된 값 반환

# 2-8. dict.setdefault(key, default=None): Returns the key value available in the dictionary

>>> dict_2 = {'key1' : 123, 

...           'key2' : 'abc', 

...           'key3' : (1, 2, 3)}

>>> 

>>> dict_2

{'key1': 123, 'key2': 'abc', 'key3': (1, 2, 3)}

>>> 

dict_2.setdefault('key1', 'No-Key')

>>> 123

>>> dict_2.setdefault('key5', 'No_Key') 

'No_Key'

>>> dict_2.setdefault('key6', None)

2.9. dict.update(dict2): 기존 사전에 새로운 사전 dict2 추가

# 2-9. dict.update(dict2): Adds dictionary dict2's key-values pairs into dict

>>> dict_5 = {'key1' : 12, 

...           'key2' : 34}

>>> dict_5

{'key1': 12, 'key2': 34}

>>> 

>>> dict_6 = {'key3' : 56}

>>> 

>>> dict_5.update(dict_6)

>>> dict_5

{'key1': 12, 'key2': 34, 'key3': 56}

 1. 사전 {키 : 값} 생성: {Key1 : Value1, Key2 : Value2, ...}

# making Dictionary with {Key1 : Value1, Key2 : Value2, ...}

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> dict_1

{'name': 'Python Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

# making a blank Dictionary { } first, and adding {Key : Value} pairs step by step using [Key] indexing

>>> dict_2 = {} # blank Dictionary

>>> dict_2['name'] = 'R Friend'

>>> dict_2['region'] = 'Seoul, Korea'

>>> dict_2['phone'] = '02-123-4567'

>>> dict_2['age'] = 20

>>> dict_2

{'name': 'R Friend', 'region': 'Seoul, Korea', 'phone': '02-123-4567', 'age': 20}

  2. 사전의 키 별 값 확인 (Accessing Values per Key in Dictionary): dict[Key]

# Accessing Values per Key in Dictionary

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> dict_1['name']

'Python Friend'

>>> dict_1['region']

'Busan, Korea'

# KeyError when there is no 'Key' in a Dictionary

>>> dict_1 = {'name' : 'Python Friend', 

...                   'region' : 'Busan, Korea', 

...                   'phone' : '010-123-9876', 

...                   'age' : 30}

>>> dict_1

{'name': 'Python Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

>>> dict_1['address'] # KeyError due to no 'address' Key in dict_1

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

KeyError: 'address'

  3. 사전 갱신 (Updating Dictionary)

# Updating Dictionary : (1) updating an existing entry, (2) adding a new entry

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> >>> dict_1['name']

'Python Friend'

>>> dict_1['name'] = 'R Friend' # (1) updating an existing entry

>>> dict_1['name']

'R Friend'

>>> 

>>> dict_1['gender'] = 'Male' # (2) Adding a new entry

>>> dict_1

{'name': 'R Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30, 'gender': 'Male'}

 4. 사전의 {키:값} 요소 삭제, 값 삭제, 사전 전체 삭제하기 (Deleting Dictionary Elements)

   : del statement, clear() method

# (4-1) Removing entry with key 'name' : del dict[Key}

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> dict_1

{'name': 'Python Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

>>> dict_1['name']

'Python Friend'

>>> del dict_1['name'] # remove entry with key 'name'

>>> dict_1['name']

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

KeyError: 'name'

# (4-2) Removing all entries in dict using dict.clear() method

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> dict_1

{'name': 'Python Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

>>> dict_1.clear()

>>> dict_1

{}

# (4-3) Deleting entire dictionary using del statement

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

>>> dict_1

{'name': 'Python Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

>>> del dict_1

>>> dict_1

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

NameError: name 'dict_1' is not defined

 5. 사전의 키 당 1개의 값 할당, 만약 사전의 키 중복 시 마지막 키의 값으로 할당 

     (In case of duplicate key in Dictionary, the last Value is assigned to the Key)

# More than one entry per key not allowed

# If keys are duplicated, then the last Value of Key will be assigned

>>> dict_1 = {'name' : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30,

...           'name' : 'R Friend'}

>>> dict_1

{'name': 'R Friend', 'region': 'Busan, Korea', 'phone': '010-123-9876', 'age': 30}

>>> dict_1['name']

'R Friend'

 6. 사전의 키는 변경 불가 (Dictionary Keys must be immutable)

    : Strings, Numbers, Tuples 은 Key로 가능, Lists 는 Key로 불가

# TypeError: unhashable type 'list'

>>> dict_1 = {['name'] : 'Python Friend', 

...           'region' : 'Busan, Korea', 

...           'phone' : '010-123-9876', 

...           'age' : 30}

Traceback (most recent call last):

  File "<stdin>", line 4, in <module>

TypeError: unhashable type: 'list'

 1-1. len(tuple) : 튜플의 전체 길이 (length)

# en() : Gives the total length of the tuple

>>> len((1, 2, 3))

3

 1-2. max(tuple) : 튜플 안에 있는 요소값 중 최대값 반환 (문자는 알파벳 기준)

# max(): Returns item from the tuple with max value

>>> len((1, 2, 3))

3

>>> max((1, 2, 3, 4, 5))

5

>>> max(('a', 'b', 'c', 'd', 'e')) # As for character, in order of alphabet

'e'

# TypeError for max() method when 'str' and 'int' are mixed in a tuple

>>> max((1, 2, 3, 'a', 'b', 'c'))

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: '>' not supported between instances of 'str' and 'int'

 1-3. min(tuple) : 튜플 안에 있는 요소값 중 최소값 반환 (문자는 알파벳 기준)

# min() : Returns item from the tuple with min value

>>> min((1, 2, 3, 4, 5))

1

>>> min(('a', 'b', 'c', 'd', 'e'))

'a'

 1-4. tuple(seq) : 리스트를 튜플로 변환 (converting a list into tuple)

# tuple(seq) : Converts a list to tuple

>>> my_list = [1, 2, 'a', 'b']

>>> type(my_list)

<class 'list'>

>>> 

>>> my_tup = tuple(my_list)

my_tup

>>> (1, 2, 'a', 'b')

>>> type(my_tup)

<class 'tuple'>

 2-1. tuple.count() : 튜플 내 요소의 개수 세기

# tuple.count(obj.) : Returns the total number of obj. in tuple

>>> tup = (1, 2, 3, 4, 5, 2, 2)

>>> tup.count(2)

3

 2-2. tuple.index(obj.) : 튜플 내 요소가 있는 위치 index 반환

# tuple.index(obj.) : Returns the index of a obj. in tuple

>>> tup = (1, 2, 3, 4, 5, 2, 2)

>>> tup.index(2)

1

[ 변경이 불가능한 자료형이 왜 필요할까? ]

 "변경이 불가능한 자료형은 변경 가능한 자료형에 비해 소프트웨어의 성능을 향상하는데 도움을 줍니다. 변경 가능한 자료형과는 달리 데이터를 할당할 공간의 내용이나 크기가 달라지지 않기 때문에 생성 과정이 간단하고, 데이터가 오염되지 않을 것이라는 보장이 있기 때문에 복사본을 만드는 대신 그냥 원본을 사용해도 되기 때문입니다. 

 사실 이런 성능보다도, 프로그래머가 자기 코드를 신뢰할 수 있다는 것이 변경이 불가능한 자료형의 가장 큰 장점입니다. 프로그래머가 수천~수만 줄의 코드를 작성하다보면 변경되지 않아야 할 데이터를 오염시키는 버그를 만들 가능성이 높습니다. 이런 실수를 몇 군데 해놓으면 어디에서 문제가 생겼는지를 찾아내기가 상당히 어렵습니다. 그래서 코드를 설계할 때부터 변경이 가능한 데이터와 그렇지 않은 데이터를 정리해서 코드에 반영하는 것이 필요합니다."

* 출처 : '뇌를 자극하는 파이썬 3', 박상현 지음, 한빛미디어

 1. 괄호와 콤마를 사용해서 튜플 만들기 (Creating tuple using parentheses or comma) : (obj, )

# tuples are encolsed within parentheses

>>> tuple_1 = ('abc', 123, 3.14, ['edf', 456], ('gh', 'st'))

>>> tuple_1

('abc', 123, 3.14, ['edf', 456], ('gh', 'st'))

>>> type(tuple_1)

<class 'tuple'>

# tuple is created by putting different comma-separated values (without parentheses)

>>> tuple_1_2 = 'abc', 123, 3.14, ['edf', 456], ('gh', 'st')

>>> tuple_1_2

('abc', 123, 3.14, ['edf', 456], ('gh', 'st'))

>>> type(tuple_1_2)

<class 'tuple'>

# creating tuple with 1 element using parentheses and a comma

>>> tuple_1_element_with_comma = (123, )

>>> tuple_1_element_with_comma

(123,)

>>> type(tuple_1_element_with_comma)

<class 'tuple'>

# if you don't include a comma for a single value, it will be a int., not a tuple

>>> int_1_element_without_comma = (123) # without a comma

>>> int_1_element_without_comma

123

>>> type(int_1_element_without_comma)

<class 'int'>

  2. 튜플 삭제(Deleting a Tuple): del tuple

# Deleting an entire Tuple with 'del' statement

>>> tuple_1 = ('abc', 123, 3.14, ['edf', 456], ('gh', 'st'))

>>> tuple_1

('abc', 123, 3.14, ['edf', 456], ('gh', 'st'))

>>> del tuple_1

>>> tuple_1 # tuple_1 is removed with del statement above

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

NameError: name 'tuple_1' is not defined

  3. 튜플 개별 요소를 변경하려면 TypeError 발생

>>> tup_1 = (1, 2, 3)

>>> tup_1[0] = 4

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: 'tuple' object does not support item assignment

 4. 튜플 인덱싱, 슬라이싱 (Tuple indexing, slicing) : tup[0], tup[0:3], tup[-1], tup[-3:-1]

# Tuple indexing and slicing start at zero

>>> tuple_2 = (1, 2, 3, 4, 5, 6, 7)

>>> tuple_2

(1, 2, 3, 4, 5, 6, 7)

>>> tuple_2[0] # Indexing one element of tuple => int.

1

>>> tuple_2[0:1] # Indexing one element of tuple => tutple

(1,)

>>> tuple_2[0:3] # Tuple slicing

(1, 2, 3)

>>> tuple_2[3:] # Tuple slicing

(4, 5, 6, 7)

# In case of negative(-), it counts from the rigth

>>> tuple_2 = (1, 2, 3, 4, 5, 6, 7)

>>> tuple_2

(1, 2, 3, 4, 5, 6, 7)

>>> tuple_2[-1] # indexing from the right

7

>>> tuple_2[-1:]

(7,)

>>> tuple_2[-3:-1] # slicing from the right

(5, 6)

>>> tuple_2[-3:]

(5, 6, 7)

 5. 여러 개 데이터를 튜플로 묶기(Tuple Packing)

          <--> 튜플의 각 요소를 여러 개 변수에 할당하기(Tuple Unpacking)

# Tuple packing

>>> tup_packing = 'Mr.Lee', 25, 'Seoul', 'KOREA'

>>> tup_packing

('Mr.Lee', 25, 'Seoul', 'KOREA')

# Tuple unpacking

>>> name, age, city, nationality = tup_packing

>>> name

'Mr.Lee'

>>> age

25

>>> city

'Seoul'

>>> nationality

'KOREA'

# if the number of unpack vaule and variable is not the same, then ValueError occurs

>>> tup_packing # 4 elements

('Mr.Lee', 25, 'Seoul', 'KOREA')

>>> name, age, city = tup_packing # 3 variables

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ValueError: too many values to unpack (expected 3)

 6. 튜플의 기본 연산자 (Basic Tuples Operations)

설명 (Description)

파이썬 코드 (Python Code) 

결과 (Results) 

 튜플 길이 (Length)

 len((1, 2, 3))

 3

 튜플 합치기 (Concatenation)

 (1, 2, 3) + ('a', 'b', 'c')

 (1, 2, 3, 'a', 'b', 'c')

 반복 (Repetition)

 (1, 'a')*3

 (1, 'a', 1, 'a', 1, 'a')

 소속 여부 (Membership)

 3 in (1, 2, 3)

 4 in (1, 2, 3)

 True

 False

 for loop 반복 (iteration)

 for x in (1, 2, 3):

    print(x)

 1

 2

 3

 1-1. len(list) : 리스트의 전체 길이

# (1-1) len(list) : Gives the total length of the list

>>> list1 = [1, 2, 3]

>>> list2 = ['a', 'b', 'c', 'd']

>>> len(list1)

3

>>> len(list2)

4

  1-2. max(list) : 리스트 안에 있는 요소 중에서 최대값 반환 (문자인 경우 알파벳 순서 기준)

# (1-2) max(list) : Returns item from the list with max value

>>> list1 = [1, 2, 3]

>>> max(list1)

3

>>> 

>>> list2 = ['a', 'b', 'c', 'd']

>>> max(list2)

'd'

  1-3. min(list) : 리스트 안에 있는 요소 중에서 최소값 반환 (문자인 경우 알파벳 순서 기준)

# (1-3) min(list) : Returns item from the list with min value

>>> list1 = [1, 2, 3]

>>> min(list1)

1

>>> 

>>> list2 = ['a', 'b', 'c', 'd']

>>> min(list2)

'a'

  1-4. list(seq) : 튜플을 리스트 자료형으로 변환

# (1-4) list(seq) : Converts a tuple into list

>>> tup = ('aaa', 'bbb', 'ccc') # tuple

>>> tup

('aaa', 'bbb', 'ccc')

>>> 

>>> list_tup = list(tup) # converting a tuple into list

>>> list_tup

['aaa', 'bbb', 'ccc']

>>> type(list_tup)

<class 'list'>

 1-5. cmp(list1, list2) : 리스크 안의 요소 비교하여 불리언값 반환 (단, Python 3.x 버전에서는 삭제됨)

# cmp() has been removed in py3.x.

>>> list1 = [1, 2, 3]

>>> list2 = ['a', 'b', 'c', 'd']

>>> list3 = [1, 2, 3]

>>> 

>>> list1 == list2

False

>>> list1 == list3 

True

  2-1. list.append(obj) : 기존 리스트에 1개의 요소를 이어 붙이기

# (2-1) list.append(obj) : Appends object obj to list

>>> list1 = [1, 2, 'a', 'b']

>>> list1.append('c') # append an element

>>> list1

[1, 2, 'a', 'b', 'c']

>>> list1.append('c', 'd') # TypeError

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: append() takes exactly one argument (2 given)

  2-2. list.extend(seq) : 기존 리스트에 다른 리스트를 이어 붙이기

# (2-2) list.extend(seq) : Appends the contents of seq to list

>>> list2 = [1, 2, 'a', 'b', 'c']

>>> list3 = [3, 3, 4, 'd', 'd']

>>> 

>>> list3.extend(list2)

>>> list3

[3, 3, 4, 'd', 'd', 1, 2, 'a', 'b', 'c']

  2-3. list.count(obj) : 리스트 안에 obj 가 몇 개 들어있는지 세어서 개수를 반환

# (2-3) list.count(obj) : Returns count of how many times obj occurs in list

>>> list3 = [3, 3, 4, 'd', 'd', 'd', 'e']

>>> list3.count(3)

2

>>> list3.count('d')

3

  2-4. list.index(obj) : 리스트에서 obj 요소 값이 있는 가장 작은 index 값 반환

# (2-4) list.index(obj) : Returns the lowest index in list that obj appears

>>> list4 = [1, 2, 'a', 'b', 'c', 'a']

>>> 

>>> list4.index('a')    

2

>>> list4.index('c')   

4

# ValueError: 'ggg' is not in list

>>> list4.index('ggg') # ValueError

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ValueError: 'ggg' is not in list

 2-5. list.insert(index, obj) : 기존 리스트의 index 위치에 obj 값을 삽입

# (2-5) list.insert(index, obj) : Inserts obj into list at offset index

>>> list5 = [1, 2, 'a', 'b', 'c']

>>> list5

[1, 2, 'a', 'b', 'c']

>>> 

>>> list5.insert(3, 'kkkk')

>>> list5

[1, 2, 'a', 'kkkk', 'b', 'c']

  2-6. list.pop(obj=list[-1]) : 기존 리스트에서 마지막 요소를 제거하고, 제거된 마지막 요소를 반환

# (2-6) list.pop(obj=list[-1]) : Removes and returns last object or obj from the list

>>> list6 = [1, 2, 'a', 'b', 'c']

>>> list6.pop() # removes the last element

'c'

>>> list6

[1, 2, 'a', 'b']

>>> list6 = [1, 2, 'a', 'b', 'c']

>>> list6.pop(2) # removes the element of the index

'a'

>>> list6

[1, 2, 'b', 'c']

 2-7. list.remove(obj) : 기존 리스트에서 remove(obj) 메소드 안의 obj 객체를 제거

# (2-7) list.remove(obj) : Removes the given object from the list

>>> list7 = [1, 2, 'a', 'b', 'c']

>>> list7.remove(1)

>>> list7

[2, 'a', 'b', 'c']

>>> 

>>> list7.remove('a')

>>> list7

[2, 'b', 'c']

# TypeError: remove() takes exactly one argument

>>> list7 = [1, 2, 'a', 'b', 'c']

>>> list7.remove(1, 'a') # TypeError

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: remove() takes exactly one argument (2 given)

 2-8. list.reverse() : 리스트의 객체를 리스트 안에서 순서를 반대로 뒤집기

# (2-8) list.reverse() : Reverses objects of list in place

>>> list8 = [1, 2, 'a', 'b', 'c']

>>> list8.reverse()

>>> 

>>> list8

['c', 'b', 'a', 2, 1]

  2-9. list.sort() : 리스트의 객체를 리스트 안에서 순서대로 정렬하기 (디폴트 오름차순)

>>> list9 = [3, 1, 9, 4, 2, 8]

>>> list9.sort() # ascending order, default setting

>>> list9

[1, 2, 3, 4, 8, 9]

>>> list9 = [3, 1, 9, 4, 2, 8]

>>> list9.sort(reverse=True) # descending order

>>> list9

[9, 8, 4, 3, 2, 1]

 1. 대괄호와 콤마로 리스트 생성 (creating a list with square brackets and comma separation)

# List : contains items separated by commas and enclosed within square brackets([])

>>> list_1 = ['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> list_1

['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

  2. 리스트 삭제 (Deleting a list) : del

>>> list_1 = ['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> list_1

['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> 

>>> del list_1

>>> list_1

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

NameError: name 'list_1' is not defined

  3. 리스트 안의 특정 위치의 값을 새로운 값으로 갱신 (Updating a list) : list[index] = value

>>> list_1

['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> list_1[1]

123

>>> list_1[1] = 111

>>> list_1

['abc', 111, 3.14, ['edf', 456], ('gh', 'st')]

  4. 리스트 인덱싱, 슬라이싱 (Indexing, Slicing a list)

# the slice operator : [:] with indexes starting at 0 in the beginning of the list

>>> list_1 = ['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> list_1

['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> 

>>> list_1[0]

'abc'

>>> list_1[0:3]

['abc', 123, 3.14]

>>> list_1[3:]

[['edf', 456], ('gh', 'st')]

>>> list_1 = ['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> list_1

['abc', 123, 3.14, ['edf', 456], ('gh', 'st')]

>>> 

>>> list_1[-1] # indexing starting from the last using '-1' : minus (-) sign

('gh', 'st')

>>> list_1[-3:-1]

[3.14, ['edf', 456]]

  5. 리스트 기본 연산자 (Basic List Operations)

설명 (description)

파이썬 표현 (python expression)

결과 (results)

 리스트 길이 (length)

 len([1, 2, 3])

 3

 리스트 합치기 (concatenation)

 [1, 2, 3] + [4, 5, 6]

 [1, 2, 3, 4, 5, 6]

 반복 (repetition)

 [1, 2, 3]*3

 [1, 2, 3, 1, 2, 3, 1, 2, 3]

 소속 여부 (membership)

 1 in [1, 2, 3]

4 in [1, 2, 3]

 True

 False

 for loop 반복 (iteration)

 for x in [1, 2, 3]: print (x);

 1 

 2 

 3 

# 신경망 모델 학습 진행 경과 확인 python code

print('Epoch:', '%04d' % (epoch + 1),

         'Avg. cost =', '{:.3f}'.format(total_cost / total_batch))

 (1) Format 을 갖춘 문자열을 만들어주는 연산자 (String Formatting Operator): %

>>> "I am %s and %d years old" %('Mr.Hong', 40)

'I am Mr.Hong and 40 years old'

%와 함께 사용하는 형식 기호

(Format Symbol with %) 

변환 (Conversion)

 %c

 문자 (character)

 %s

 str() 메소드를 사용해서 문자열로 변환한 후 formatting

%i 

 부호가 있는 십진법 정수 (signed decimal integer)

 %d

 부호가 있는 십진법 정수 (signed decimal integer)

 %u

 부호가 없는 십진법 정수 (unsigned decimal integer)

 %o

 8진법 정수 (octal integer)

 %x

 소문자의 16진법 정수 (hexadecimal integer, lowercase letters)

 %X

 대문자의 16진법 정수 (hexadecimal integer, UPPERcase letters)

 %e

 소문자 'e'를 사용한 지수 표기 (exponential notation with lowercase 'e')

 %E

 대문자 'E'를 사용한 지수 표기 (exponential notation with UPPERcase 'E')

 %f

 부동소수형 실수 (floating point real number)

 %g

 %f(부동소수형 실수)와 %e (소문자 'e' 지수 표기) 의 단축형 표기

 %G

 %f(부동소수형 실수)와 %E(대문자 'E' 지수 표기)의 단축형 표기

>>> "I am %s and %d years old" %('Mr.Hong', '40')  # '40' is not a number, but a string

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: %d format: a number is required, not str

>>> "%04d" % (5)

'0005'

>>> "%04d" % (55)

'0055'

>>> "%04d" % (555)

'0555'

>>> "%04d" % (5555)

'5555'

>>> "%04d" % (55555)

'55555'

>>> "%.3f" % (5)

'5.000'

>>> "%.3f" % (0.5)

'0.500'

>>> "%.3f" % (0.55)

'0.550'

>>> "%.3f" % (0.555)

'0.555'

>>> "%.3f" % (0.5555)

'0.555'

>>> print('Epoch:', '%04d' % (100),

...       'Avg. cost =', '{:.3f}'.format(10 / 1000))

Epoch: 0100 Avg. cost = 0.010

In [1]: import pandas as pd

In [2]: df = pd.DataFrame({'id': ['a', 'b', 'c', 'd'],

   ...: 'val': [1.045, 5.200, 0.051, 8.912]})

In [3]: df

Out[3]:

  id    val

0  a  1.045

1  b  5.200

2  c  0.051

3  d  8.912

In [4]: formater = lambda x:" %.2f" %(x)

In [5]: df['val'] = df['val'].map(formater)

In [6]: df

Out[6]:

  id    val

0  a   1.04

1  b   5.20

2  c   0.05

3  d   8.91

 (2) Format 을 갖춘 문자열을 만들어주는 메소드 (String Formatting Method): format()

>>> "I am {name} and {age} years old".format(name='Mr.Hong', age=40)

'I am Mr.Hong and 40 years old'

>>> "I am {name} and {age} years old".format(age=40, name='Mr.Hong')

'I am Mr.Hong and 40 years old'

>>> "I am {0} and {1} years old".format('Mr.Hong', 40)

'I am Mr.Hong and 40 years old'

>>> "I am {0} and {1} years old".format(40, 'Mr.Hong') # sequence matters

'I am 40 and Mr.Hong years old'