Tuple in Python (5)

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*Memo:

• My post explains a tuple (1).
• My post explains a tuple (2).
• My post explains a tuple (3).
• My post explains a tuple (4).

A tuple cannot be changed by indexing, slicing and a del statement as shown below:

*Memo:

• A del statement cannot remove zero or more elements from a tuple by indexing and slicing but can remove one or more variables themselves.

v = ('a', 'b', 'c', 'd', 'e', 'f')

v[1] = 'X'
v[-5] = 'X'
v[3:5] = ['Y', 'Z']
v[-3:-1] = ['Y', 'Z']
v[1], v[3:5] = 'X', ['Y', 'Z']
v[-5], v[-3:-1] = 'X', ['Y', 'Z']
# TypeError: 'tuple' object does not support item assignment

v = ('a', 'b', 'c', 'd', 'e', 'f')

del v[1], v[3:5]
# del v[-5], v[-2:5]
# TypeError: 'tuple' object does not support item deletion

v = ('a', 'b', 'c', 'd', 'e', 'f')

del v

print(v)
# NameError: name 'v' is not defined

If you really want to change a tuple, use list() and tuple() as shown below:

v = ('a', 'b', 'c', 'd', 'e', 'f')

v = list(v)

v[1] = 'X'
v[-5] = 'X'
v[3:5] = ['Y', 'Z']
v[-3:-1] = ['Y', 'Z']

v[1], v[3:5] = 'X', ['Y', 'Z']
v[-5], v[-3:-1] = 'X', ['Y', 'Z']

v = tuple(v)

print(v)
# ('a', 'X', 'c', 'Y', 'Z', 'f')

v = ('a', 'b', 'c', 'd', 'e', 'f')

v = list(v)

del v[1], v[3:5]
# del v[-5], v[-2:5]

v = tuple(v)

print(v)
# ('a', 'c', 'd')

A tuple can be continuously used through multiple variables as shown below:

v1 = v2 = v3 = ('A', 'B', 'C', 'D', 'E') # Equivalent
                                         # v1 = ('A', 'B', 'C', 'D', 'E')
print(v1) # ('A', 'B', 'C', 'D', 'E')    # v2 = v1
print(v2) # ('A', 'B', 'C', 'D', 'E')    # v3 = v2
print(v3) # ('A', 'B', 'C', 'D', 'E')

A tuple cannot be shallow-copied and deep-copied as shown below:

<Shallow & Deep copy>:

*Memo:

• v1 and v2 refer to the same outer and inner tuple.
• is keyword can check if v1 and v2 refer to the same outer and inner tuple.
• copy.copy(), tuple() and slicing cannot shallow-copy a tuple.
• copy.deepcopy() cannot deep-copy and even shallow-copy a tuple.

import copy

v1 = ('A', 'B', ('C', 'D'))
v2 = copy.copy(v1)
v2 = tuple(v1)
v2 = v1[:]
v2 = copy.deepcopy(v1)

print(v1) # ('A', 'B', ('C', 'D'))
print(v2) # ('A', 'B', ('C', 'D'))

print(v1 is v2, v1[2] is v2[2])
# True True