This question already has answers here:
How can I put an actual backslash in a string literal (not use it for an escape sequence)?
(4 answers)
Closed 7 years ago.
How do i escape \n in a string in python.
How do i write out to stdin in python this string "abc\ndef" as one single input
Sys.stdout.write("abc\ndef")
current output
import sys
>>> sys.stdout.write("abc\ndef")
abc
def
I would like it to be abc\ndef
You should escape the backslash so that it's not treated as escaping character itself:
Sys.stdout.write("abc\\ndef")
Background
The backslash \ tells the parser that the next character is something special and must be treated differently. That's why \n will not print as \n but as a newline. But how do we write a backslash then? We need to escape it, too, resulting in \\ for a single backslash and \\n for the output \n.
Docs here, also see this SO question
Alternatively you can use "raw" strings, i.e. prefixing your strings with an r, to disable interpreting escape sequences is your strings:
Sys.stdout.write(r"abc\ndef")
As an alternative to escaping the backslash, you can disable backslash-escaping entirely by using a raw string literal:
>>> print(r"abc\ndef")
abc\ndef
Related
When I write print('\') or print("\") or print("'\'"), Python doesn't print the backslash \ symbol. Instead it errors for the first two and prints '' for the third. What should I do to print a backslash?
This question is about producing a string that has a single backslash in it. This is particularly tricky because it cannot be done with raw strings. For the related question about why such a string is represented with two backslashes, see Why do backslashes appear twice?. For including literal backslashes in other strings, see using backslash in python (not to escape).
You need to escape your backslash by preceding it with, yes, another backslash:
print("\\")
And for versions prior to Python 3:
print "\\"
The \ character is called an escape character, which interprets the character following it differently. For example, n by itself is simply a letter, but when you precede it with a backslash, it becomes \n, which is the newline character.
As you can probably guess, \ also needs to be escaped so it doesn't function like an escape character. You have to... escape the escape, essentially.
See the Python 3 documentation for string literals.
A hacky way of printing a backslash that doesn't involve escaping is to pass its character code to chr:
>>> print(chr(92))
\
print(fr"\{''}")
or how about this
print(r"\ "[0])
For completeness: A backslash can also be escaped as a hex sequence: "\x5c"; or a short Unicode sequence: "\u005c"; or a long Unicode sequence: "\U0000005c". All of these will produce a string with a single backslash, which Python will happily report back to you in its canonical representation - '\\'.
This question already has answers here:
Why can't Python's raw string literals end with a single backslash?
(13 answers)
Closed 7 months ago.
The current Python grammar doesn't allow one to output a trailing \ in a raw string:
>>> print(r'a\b\c\')
SyntaxError: EOL while scanning string literal
On the contrary, you can write Bash like this:
echo 'a\b\c\'
I understand what the doc is saying. I wouldn't feel strange if an expression '\' fails because the backslash is escaping the quote. What I'm questioning is r'\': Aren't raw strings meant to be raw (which means backslashes in the string are taken literally)?
Do we have to write r'a\b\c' + '\\' or 'a\\b\\c\\' to make a string literal a\b\c\ in Python? I couldn't see how this is Pythonic.
From the documentation,
Specifically, a raw string cannot end in a single backslash (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the string, not as a line continuation.
The limitation is due to the fact that you need someway to include a ' inside a raw string. Otherwise there is no way to put bob said "I'm not hungry" in a string.
So you end up in weird situation where you need an escape character for this case. So in raw strings you escape a ' with a \ and yes the \ stays in the string.
So r'bob said "I\'m not hungry"' it is!!
When you write print(r'\'), Python understand \' in that statement as a character. Because of that python raised syntax error because the there is a incomplete string inside print function.
For an example if you need to print i am "free" man , you should write
print("i am \"free\" man")
This question already has answers here:
Can't escape the backslash with regex?
(7 answers)
Closed 7 years ago.
This explanation is from the python documentation:
Both string and bytes literals may optionally be prefixed with a letter 'r' or 'R'; such strings are called raw strings and treat backslashes as literal characters. As a result, in string literals, '\U' and '\u' escapes in raw strings are not treated specially. Given that Python 2.x’s raw unicode literals behave differently than Python 3.x’s the 'ur' syntax is not supported.
If raw strings treat backslashes as char literals, why does the backslash need to be escaped in the expression:
re.compile(r"'\\'")
Instead of just being able to write:
re.compile(r"'\'")
To capture a single backslash when using the re module?
because '\' has special meaning in re it means escape the character after it in the language you use to define a re so if you want to match '+' as a character your re will be '\+'
This question already has answers here:
How can I put an actual backslash in a string literal (not use it for an escape sequence)?
(4 answers)
Closed 8 years ago.
I program in Python in PyCharm and whenever I write '\' as a string it says that the following statements do nothing. For example:
Is there a way to fix this and make it work?
Thanks.
You need to double the backslash:
'/-\\'
as a single backslash has special meaning in a Python string as the start of an escape sequence. A double \\ results in the string containing a single backslash:
>>> print '/-\\'
/-\
If the backslash is not the last character in the string, you could use a r'' raw string as well:
>>> print r'\-/'
\-/
You need to scape them to be in the string, for example:
>>>s='\\'
>>>print s
\
You can also use the r (raw string) modifier in front of the string to include them easily but they can't end with an odd number of backslash. You can read more about string literals on the docs.
This question already has answers here:
Why can't Python's raw string literals end with a single backslash?
(14 answers)
Python Literal r'\' Not Accepted [duplicate]
(5 answers)
Closed 9 years ago.
I was under the impression that in Python a raw string, written as r'this is a raw string' would omit any escape characters, and print EXACTLY what is between the quotes. My problem is that when I try print r'\' I get SyntaxError: EOL while scanning string literal. print r'\n' correctly prints \n, though.
Quoting the documentation:
When an 'r' or 'R' prefix is present, a character following a backslash is included in the string without change, and all backslashes are left in the string. For example, the string literal r"\n" consists of two characters: a backslash and a lowercase 'n'. String quotes can be escaped with a backslash, but the backslash remains in the string; for example, r"\"" is a valid string literal consisting of two characters: a backslash and a double quote; r"\" is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, a raw string cannot end in a single backslash (since the backslash would escape the following quote character).
Added emphasis mine.
Raw strings thus do attach some meaning to a backslash, but only where quotes are concerned.
From the Python docs:
If we make the string literal a “raw” string, \n sequences are not converted to newlines, but the backslash at the end of the line, and the newline character in the source, are both included in the string as data.
You have the wrong idea about raw strings.