Python: array and print() format

Question

I am trying to implement a function that changes array_1 to array_2, so that array_2 produces the same output as array_1. For example:

for item in array_1: 
    print(item, end ='')

I want the code below to produce the same output as the code above:

for item in array_2:
    print(item)

array_1 = ["Hello", "World", '\n', '\n', "This", "is", '\n', "a", "textarray"]

Running this through the first code gives me:

HelloWorld

Thisis
atextarray

How should I implement the function that changes array_1 to array_2 so that it produces the same output above?

array_2 is undefined. I want to build array_2 from array_1 so it negates what print(item, end =' ') is doing and use print(item) instead. — Corp. and Ltd.
– Corp. and Ltd., Commented Jul 18, 2018 at 0:55
Since print without the other parameters will force a newline at the end of the printing, you need to properly concatenate the elements of array_1 into a single string. Visit your favorite tutorial for information on basic string operations. — Prune
– Prune, Commented Jul 18, 2018 at 0:56
@Prune That still doesn't solve the problem, because there's still going to be one extra newline at the end of the loop. There really is no way around this. — abarnert
– abarnert, Commented Jul 18, 2018 at 0:59

blhsing · Accepted Answer · 2018-07-18 01:54:53Z

2

Since all you're really looking for is to change the default behavior of print so that it doesn't output a trailing newline by default, you can use functools.partial to make end='' a default parameter instead. This way, you don't need to worry about creating a new list from array_1.

from functools import partial
print = partial(print, end='')
array_1 = ["Hello", "World", '\n', '\n', "This", "is", '\n', "a", "textarray"]
for item in array_1:
    print(item)

This outputs:

HelloWorld

Thisis
atextarray

edited Jul 18, 2018 at 1:54

answered Jul 18, 2018 at 1:36

blhsing

109k9 gold badges88 silver badges132 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

abarnert · Accepted Answer · 2018-07-18 01:02:28Z

1

What you want is impossible.

First, notice that the reverse direction would be easy. The difference is that the items in array2 are printed with a newline after each one, while the items in array1 are printed with nothing after each one, so all you'd need to do is add a \n to the end of each item in array_1.

array_2 = [item+'\n' for item in array_1]

You can't just reverse that. There's obviously nothing like item-'\n'. It every item happened to end with a \n, you could do item[:-1], but most of them don't, and you can't remove a newline that isn't there.

And there's no way to cancel out the newline that print is going to add after the string with an anti-newline. I mean, you could include a terminal control sequence to move the cursor up one line so it kind of looks like it did the same thing, but it's not actually doing the same thing, and that would be ridiculously easy to break (run the code on Windows, redirect the output to a file, …).

You can get pretty close. You never said that you need the elements to be in one-to-one correspondence, so you can just do this:

array_2 = [''.join(array_1)]

Now you've just got one item in array_2, so the fact that it's printing newlines between the items doesn't matter.

But there's still a newline at the end, after all one items. And still no way to get rid of that (since the last item doesn't end in a \n that you can remove).

So, the problem is impossible. (Short of trick-question answers like redefining print to special-case your output or something.)

edited Jul 18, 2018 at 1:02

answered Jul 18, 2018 at 0:51

abarnert

368k54 gold badges626 silver badges691 bronze badges

2 Comments

Corp. and Ltd. Over a year ago

I am not necessarily trying to remove a newline. I am trying to format array_1 such that we can work around creating the newline.

abarnert Over a year ago

@Corp.andLtd. I get that, and that's the point: There's no way to do that. The newline is added by print, it's not part of the strings. Therefore, nothing you can do to the strings will prevent the newline from being printed.

Collectives™ on Stack Overflow

Python: array and print() format

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related