데이터 구조 및 분석 ch_1_9 Assignment and Equivalence

Jul 4, 2021 » writing

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ch_1_9 Assignment and Equivalence

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Assignment and Equivalence

1. Assignment and Equivalence
: One variable's value is changed
: But, you see three changes
: Becuase
- reference
- x has two references from y and z
- values of y and z are determined by x
- x is changed
: "=="checks the equivalence of two referenced values (두개의 레퍼런스)
: "is" checks the equivalence of two referenced objets' IDs (같은 위치)

x = [1, 2, 3]
Y = [100, x, 120]   # nested (둥지속)
z = [x, 'a', 'b']

print('x is ', x)
print('Y is ', Y)
print('z is ', z)

x[1] = 2021
print('\nx is ', x)
print('Y is ', Y)
print('z is ', z)

x[1] = 2
x2 = [1,2,3]

if x == x2:
    print('Values are equivalent')
else :
    print('Values are not equivalent')
if x is x2 :
    print('Values are stored at the same place')
else :
    print('Values are not stored at the same place')
if x[1] is Y[1][1] :
    print('Values are stored at the same place')
else :
    print('Values are not stored at the same place')

# x is  [1, 2, 3]
# Y is  [100, [1, 2, 3], 120]
# z is  [[1, 2, 3], 'a', 'b']

# x is  [1, 2021, 3]
# Y is  [100, [1, 2021, 3], 120]
# z is  [[1, 2021, 3], 'a', 'b']
# Values are equivalent
# Values are not stored at the same place
# Values are stored at the same place