How do I change elements in a list?

[Just Another Victim of the Ambient Morality]

How do you change certain elements in a list? I'm looking to do the
Python equivalent of this Ruby code:


-> first = [1, 2]
=> [1, 2]
-> second = first
=> [1, 2]
-> first.map! {|i| i + 1}
=> [2, 3]
-> first
=> [2, 3]
-> second
=> [2, 3]


I need to change a list, in place, so other variables referencing that
list also see the change.
Thank you...

 

[kyosohma]

How do you change certain elements in a list? I'm looking to do the
Python equivalent of this Ruby code:

-> first = [1, 2]
=> [1, 2]
-> second = first
=> [1, 2]
-> first.map! {|i| i + 1}
=> [2, 3]
-> first
=> [2, 3]
-> second
=> [2, 3]

I need to change a list, in place, so other variables referencing that
list also see the change.
Thank you...

You can "point" one variable name at another so that they both
reference the same list:

second = first

To change a list "in place", I usually do something like this:

first[someElement] = something-else

or

# change the first element in the list
first[0] = 55

See also

http://docs.python.org/tut/node7.html
http://www.diveintopython.org/native_data_types/lists.html
http://docs.python.org/lib/built-in-funcs.html

Mike

 

[Dan]

How do you change certain elements in a list? I'm looking to do the
Python equivalent of this Ruby code:

-> first = [1, 2]
=> [1, 2]
-> second = first
=> [1, 2]
-> first.map! {|i| i + 1}
=> [2, 3]
-> first
=> [2, 3]
-> second
=> [2, 3]

I need to change a list, in place, so other variables referencing that
list also see the change.
Thank you...

first = [1,2]
second = first
for i in range(len(first)):

first += 1

first [2, 3]
second

[2, 3]

-Dan

 

[Bruno Desthuilliers]

Just Another Victim of the Ambient Morality a écrit :

How do you change certain elements in a list? I'm looking to do the
Python equivalent of this Ruby code:


-> first = [1, 2]
=> [1, 2]
-> second = first
=> [1, 2]
-> first.map! {|i| i + 1}
=> [2, 3]
-> first
=> [2, 3]
-> second
=> [2, 3]


I need to change a list, in place, so other variables referencing that
list also see the change.

first = [1,2]
second = first
first[:] = [i+1 for i in first]

HTH