Python Tuples

Python Tuples

Python tuples are

• ordered collections of arbitrary objects
• immutable sequence

why do we need tuples if we have lists?

• list as a data structure that changes over time
• tuple as a simple association of objects (frequent use for a row in a relational database table)

'''Tuples in Action'''

# ------- basic ------- #
x = (40)                                    # an integer
y = (40,)                                   # a one-item tuple

# ------- sequence-shared operations ------- #
T1 = (1, 2) + (3, 4)                        # concatenation
T2 = (1, 2) * 4                             # repetition
element = T1[0]                             # indexing
section = T1[1:3]                           # slicing

# ------- tuple methods ------- #
T = (1, 2, 3, 2, 4, 2)
print(T.index(2),                           # offset of first appearance of 2
    T.index(2, 2),                          # offset of appearance after offset 2
    T.count(2))                             # how many 2s are there?

# ------- one-level-deep immutability ------- #
nested = (1, [2, 3], 4)
try:
    nested[1] = 'spam'
except Exception as e:
    print(e)                                # 'tuple' object does not support item assignment
nested[1][0] = 'spam'                       # this works: can change mutables inside

Python Tuples

原文：https://www.cnblogs.com/bit-happens/p/12163846.html