Replacing a text with \n in it, with a real \n output [duplicate]

Question

I am trying to get a config from a juniper router and I have the following problem:

After setting this

stdin, stdout, stderr = client1.exec_command('show configuration interfaces %s' % SID)
 CONFIG = stdout.read()
 print CONFIG

It brings me something like these

'description El_otro_Puerto_de_la_Routing-instance;\nvlan-id 309;\nfamily inet {\n    mtu 1600;\n    address 10.100.10.10/24;\n}\n'

and the problem is that I want to receive that information in this format:

'description El_otro_Puerto_de_la_Routing-instance;
 nvlan-id 309;
 nfamily inet {
  mtu 1600;
  address 10.100.10.10/24;
 }

So I want the \n to actually be a new line, and not just to show me the "\n" string.

Engrossing

What does print repr(CONFIG) show? – Sulphathiazole

Does the string print with quotation marks in it? Looks like it's a string representation of a string. – Constipate

See #24886623 – Vanden

Related: #48908631 – Roadhouse

Answer 1

If you're running this in the Python interpreter, it is the regular behavior of the interpreter to show newlines as "\n" instead of actual newlines, because it makes it easier to debug the output. If you want to get actual newlines within the interpreter, you should print the string you get.

If this is what the program is outputting (i.e.: You're getting newline escape sequences from the external program), you should use the following:

OUTPUT = stdout.read()
formatted_output = OUTPUT.replace('\\n', '\n').replace('\\t', '\t')
print formatted_output

This will replace escaped newlines by actual newlines in the output string.

Gerber

I'd like to use eval() for supporting parsing any possible escape sequence. for example: formatted_output=eval("'{}'".format(OUTPUT) – Photic

Never run eval() on untrusted input. – Gerber

Answer 2

In python 3+, the best way to interpret all escape characters is:

print(f"{yourStringHere}")

This uses f-strings which, in my opinion, is probably the most elegant way to solve this issue.

Oppilate

New to f-strings... but this doesn't work for me (3.7). Have I missed something? >>> mystring = r"this\nthat\tthe other" >>> print(f"{mystring}") this\nthat\tthe other – Chloropicrin

Answer 3

An alternative to what you want is splitting your string into a list of strings (per line).

mystr = 'a\nb\nc'
mystr = mystr.split(sep='\n')
print(mystr)
#this will be your print output:['a', 'b', 'c']
for s in mystr:
    print(s)
#your print output:
#a
#b
#c

Liquidate

I believe this was not the author's question. I believe what they were trying to do was to replace the escape sequence '\n' by an actual newline character. – Gerber

Read where it says "an alternative to what you want". The person has not said if this question refers specifically to the interpreter, a console (cmd in windows), or writing to file. – Liquidate

Agree that this is useful. As an efficiency improvement we could replace the loop with print("\n".join(map(str, mystr))) – Potted

Answer 4

A regular expression can help with locating the \x sequences. The substitution-pairs will still have to be specified manually though, just like in @PedroCastilho's answer.

import re
CONFIG = stdout.read()
print(re.sub(r'\\.',lambda x:{'\\n':'\n','\\t':'\t'}.get(x[0],x[0]),CONFIG))

This will replace \\n-s and \\t-s with actual line breaks and tabulators, and leaves the unknown ones intact.

Like

print(re.sub(r'\\.',lambda x:{'\\n':'\n','\\t':'\t'}.get(x[0],x[0]),
      'foo\\nbar\\nbaz\\tbrr\\n\\q'))

prints

foo
bar
baz     brr
\q

So line breaks and the tabulator are in place, and \q simply survived.

Basuto