How do you input escape sequences in Python?

Question

Say you make the following program

a=input("Input: ")
print(a)

and try to input the newline character, \n:

Input: a\nb
a\nb

The input has not been treated as the \n character but rather as two separate characters, \\ and n. How do you get an input with an escape sequence to be treated as an escape sequence? The result for the sample above should be

Input: a\nb
a
b

BoarGules · Accepted Answer · 2019-01-28T22:23:30.960

4

The input statement takes the input that the user typed literally. The \-escaping convention is something that happens in Python string literals: it is not a universal convention that applies to data stored in variables. If it were, then you could never store in a string variable the two characters \ followed by n because they would be interpreted as ASCII 13.

You can do what you want this way:

import ast
import shlex
a=input("Input: ")
print(ast.literal_eval(shlex.quote(a)))

If in response to the Input: prompt you type one\ntwo, then this code will print

one
two

This works by turning the contents of a which is one\ntwo back into a quoted string that looks like "one\ntwo" and then evaluating it as if it were a string literal. That brings the \-escaping convention back into play.

But it is very roundabout. Are you sure you want users of your program feeding it control characters?

edited Jan 28 '19 at 22:23

answered Jan 28 '19 at 22:11

BoarGules

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What if the input string contains `"`? – Primusa Jan 28 '19 at 22:12
@BobSmith I can say this with confidence because that stuff was pasted out of IDLE: Your syntax error is probably because you are running Python < 3.7; `f`-strings are new. But I've done an edit that will work in any version of Python 3. And fixes the issue that @Primusa pointed out. – BoarGules Jan 28 '19 at 22:25
@Primusa Fixed the bug you reported. – BoarGules Jan 28 '19 at 22:25
@BoarGules whoa this is great! I wish i could upvote twice. – Primusa Jan 28 '19 at 22:34
@Bishop I think that objections to `eval()` are often exaggerated and implausible but in this case there really is no discussion. – BoarGules Jan 28 '19 at 22:35
@BoarGules Can't but agree. – incalite Jan 28 '19 at 22:36
@Primusa Thanks for the astute bug report. That made the solution much better. – BoarGules Jan 28 '19 at 22:36

busybear · Answer 2 · 2019-01-28T22:22:02.533

2

You can replace \\n with \n to get the result you want:

a = a.replace('\\n', '\n')

input won't read \ as an escape character.

If you are just interested in printing the input, you can use something like this, which will handle other escape characters. It's not an ideal solution in my opinion and also suffers from breaking with '.

eval('print("{}")'.format(a))

edited Jan 28 '19 at 22:22

answered Jan 28 '19 at 22:05

busybear

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What about something with `\t`? – Primusa Jan 28 '19 at 22:07
1

@Primusa press tab when giving the input? \n is special because pressing return closes the input – user24343 Jan 28 '19 at 22:16

score 1 · Answer 3 · edited Aug 25 '21 at 15:42

1

Hi you can't input \n as it would result in the input closing. Here is what you can try :

use replace to post-process the string

input().replace("\\n", "\n")

use while to input until you get an empty line

inputs = []
current = input()
while current:
    inputs.append(current)
    current = input()
"\n".join(inputs)

edited Aug 25 '21 at 15:42

Balu

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answered Jan 28 '19 at 22:06

Benoît P

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score 0 · Answer 4 · answered Nov 19 '21 at 12:35

Python can do this natively:

text = r"Hello\nworld!"
text = text.encode().decode( "unicode_escape" )
print( text )

Note that your shell's (shlex) escaping - if any - may differ from Python's own escape protocol, which is used for parsing the strings in user code.

How do you input escape sequences in Python?

4 Answers4

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