Altering a copy of a list-CodePudding

I want to alter a copy of a list without altering the original list. My code shows that the copy is stored at a different memory address from the original. But the original list is altered along with the copy. What am I doing wrong?

original = ['Humpty', 'Dumpty'],['Jack', 'Sprat']
revised = list(original[:])

# Reverse a name on the revised list.
# Don't alter the original list.
revised[0][0],revised[0][1]=revised[0][1],revised[0][0]

print(f"\nThe original list:\t{original}\nAnd its address:\t{id(original)}")
print(f"\nThe revised list:\t{revised}\nAnd its address:\t{id(revised)}\n")

Output:

The original list:  (['Dumpty', 'Humpty'], ['Jack', 'Sprat'])
And its address:    140586839997408

The revised list:   [['Dumpty', 'Humpty'], ['Jack', 'Sprat']]
And its address:    140586839996848

(I'm running Python 3.7.4.)

CodePudding user response：

You need to copy the values of the inner list.

original = [['Humpty', 'Dumpty'], ['Jack', 'Sprat']]
revised = [ar[:] for ar in original]

# Reverse a name on the revised list.
# Don't alter the original list.
revised[0][0], revised[0][1] = revised[0][1], revised[0][0]

print(f"\nThe original list:\t{original}\nAnd its address:\t{id(original)}")
print(f"\nThe revised list:\t{revised}\nAnd its address:\t{id(revised)}\n")

Output:

The original list:  [['Humpty', 'Dumpty'], ['Jack', 'Sprat']]
And its address:    140210727731136
The revised list:   [['Dumpty', 'Humpty'], ['Jack', 'Sprat']]
And its address:    140210729012672