How to modify sequence of strings?-CodePudding

Let's consider very simple probem, if I have list:

x = ["a", "b", "c", "d", "e"]

and I want to transform it by adding "_x" at the end of string. In other words I desirable output is:

x = ["a_x", "b_x", "c_x", "d_x", "e_x"]

Of course I can just loop over strings:

for i in range(len(x)):
    x[i] = x[i]   "_x"

But I'm searching of more efficient solution. Could you please give me a hand with doing so?

CodePudding user response：

If you want to modify the list in-place, the only "better" solution is a listcomp that is assigned back to the complete slice of the original list:

x[:] = [item   '_x' for item in x]

which, unlike:

x = [item   '_x' for item in x]

will modify any aliases that refer to the same original list (e.g. if a caller passes such a list to a function, the former will modify the caller's list as well, the latter will not).

CodePudding user response：

You can use list comprehensions :

print([item   '_x' for item in x])
print([f"{item}_x" for item in x])

It's a little bit faster than loops, but definitely more readable.

list comprehensions create new lists, they don't modify the existing list. You can then rebind the result to x or do a slice assignment like x[:] = ...

CodePudding user response：

You can also use map():

[In] list(map(lambda x: x   '_x', your_list))

[Out] ['a_x', 'b_x', 'c_x', 'd_x', 'e_x']

CodePudding user response：

For in-place modification of the list you can combine map with subscript assignment:

x = ["a", "b", "c", "d", "e"]

x[:] = map("{}_x".format,x)

print(x)
['a_x', 'b_x', 'c_x', 'd_x', 'e_x']