Reset a modified list to previous value on iPython

Question

I'd like to substitue '(', ')' with '[', ']' in the folliwing list using slicing.

    # the raw data 
    square = ['(', ')', '.', '^', '-']
    # the result I want
    square = ['[', ']', '.', '^', '-']

Replace with slicing method

    In [45]: square[:1] = ['[', ']']
    In [46]: square
    Out[46]: ['[', ']', ']', '.', '^', '-']
  # sliced with wrong index, it should be [:2]

I have to manipulate on the modified square like:

 square.remove(']')

Or re-assign to square manually

    In [47]: square = ['(', ')', '.', '^', '-']
        ...: square[:2] = ['[', ']']
    In [48]: square
    Out[48]: ['[', ']', '.', '^', '-']

During the process, how to reset the modified square to its unmodified status?

I'm not sure if this is what you are asking, but the list maintains no knowledge of previous state. There is no "reset". — juanpa.arrivillaga, Mar 26 '18 at 09:27

Pitto · Accepted Answer · 2018-03-26T20:58:44.070

2

I would create a new list from the old one using list()

square = ['(', ')', '.', '^', '-']
backup_square = list(square)
# Here I take the 1st value from square list and I put different data in it
square[0] = "DIFFERENT VALUE"

You will then be able to access the previous version of square in backup_square

print backup_square
>>> ['(', ')', '.', '^', '-']

edited Mar 26 '18 at 20:58

answered Mar 26 '18 at 09:30

Pitto

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Reset a modified list to previous value on iPython

1 Answers1