This question already has answers here:
Escaping regex string
(4 answers)
Closed 7 months ago.
I'm trying to escape the characters -]\^$*. each with a single backslash \.
For example the string: ^stack.*/overflo\w$arr=1 will become:
\^stack\.\*/overflo\\w\$arr=1
What's the most efficient way to do that in Python?
re.escape double escapes which isn't what I want:
'\\^stack\\.\\*\\/overflow\\$arr\\=1'
I need this to escape for something else (nginx).
This is one way to do it (in Python 3.x):
escaped = a_string.translate(str.maketrans({"-": r"\-",
"]": r"\]",
"\\": r"\\",
"^": r"\^",
"$": r"\$",
"*": r"\*",
".": r"\."}))
For reference, for escaping strings to use in regex:
import re
escaped = re.escape(a_string)
Just assuming this is for a regular expression, use re.escape.
We could use built-in function repr() or string interpolation fr'{}' escape all backwardslashs \ in Python 3.7.*
repr('my_string') or fr'{my_string}'
Check the Link: https://docs.python.org/3/library/functions.html#repr
re.escape doesn't double escape. It just looks like it does if you run in the repl. The second layer of escaping is caused by outputting to the screen.
When using the repl, try using print to see what is really in the string.
$ python
>>> import re
>>> re.escape("\^stack\.\*/overflo\\w\$arr=1")
'\\\\\\^stack\\\\\\.\\\\\\*\\/overflo\\\\w\\\\\\$arr\\=1'
>>> print re.escape("\^stack\.\*/overflo\\w\$arr=1")
\\\^stack\\\.\\\*\/overflo\\w\\\$arr\=1
>>>
Simply using re.sub might also work instead of str.maketrans. And this would also work in python 2.x
>>> print(re.sub(r'(\-|\]|\^|\$|\*|\.|\\)',lambda m:{'-':'\-',']':'\]','\\':'\\\\','^':'\^','$':'\$','*':'\*','.':'\.'}[m.group()],"^stack.*/overflo\w$arr=1"))
\^stack\.\*/overflo\\w\$arr=1
Utilize the output of built-in repr to deal with \r\n\t and process the output of re.escape is what you want:
re.escape(repr(a)[1:-1]).replace('\\\\', '\\')
Related
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 1 year ago.
I need to split a string that I receive like that :
my_string = "\data\details\350.23.43.txt"
when I use my_string.replace ("\\", "/")
it returns : /data/detailsè.23.43.txt
It's considering the \350 in my string as a special character 'è'
Edit after your comment:
Try
my_string = r"\data\details\350.23.43.txt"
That happens because \ooo is interpreted as a character with octal value as described in the docs.
I guess the only way is to escape the \ as in:
my_string = "\data\details\\350.23.43.txt"
Then you can do stuff like:
my_string.split("\\")
Where do you get the string from? Is there a way to influence that?
And this looks like a path. It would be better to use
os.path.join("data", "details", "350.23.43.txt")
to create paths independently of the operating system.
\ in string literals are treated as escaping chars. That is why s1 = "line\nsecond line" creates a string with two lines. That is also why you use "\\" in my_string.replace ("\\", "/").
So to fix your problem, if you're using a string literal my string = "\data\details\350.23.43.txt" you should instead use "\\data\\details\\350.23.43.txt" to make sure your \ are properly escaped. Alternatively, you can use a raw string my string = r"\data\details\350.23.43.txt" by prepending r to the quote. That way nothing gets escaped (so r"\n" would be a 2 char string with \ and n instead of just a single new line char)
This question already has answers here:
Confused about backslashes in regular expressions [duplicate]
(3 answers)
Closed 5 years ago.
>>> import re
>>> a='''\\n5
... 8'''
>>> b=re.findall('\\n[0-9]',a)
>>> print(b)
['\n8']
Why does it show \n8 and not \n5?
I used a \ in front of \n the first time.
I am finding the use of raw string in regex in python a bit confusing. To me it does not seem to be making any changes to the result
This is because in strings, the newline character is considered that, a single character.
When you do \\n5 you're escaping the \, so that's literally printing \n5, and not a newline by Python standards.
When you search for a regex such as \\n[0-9] though, in the first \ you're escaping the \n regex expression, so in the end you're looking for \n which is Python's newline. That matches the actual newline in your string, but not \\n which is two separate characters, an escaped \ and an n.
\\n is not a newline, it's an escaped backslash with an n.
>>> import re
>>> a = '''\n5
... 8'''
>>> a=re.findall('\\n[0-9]',a)
>>> print(a)
['\n5', '\n8']
because \\n5 is not valid new line, it will print \n5
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
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:
How can I put an actual backslash in a string literal (not use it for an escape sequence)?
(4 answers)
Closed 7 months ago.
In python, I am trying to replace a single backslash ("\") with a double backslash("\"). I have the following code:
directory = string.replace("C:\Users\Josh\Desktop\20130216", "\", "\\")
However, this gives an error message saying it doesn't like the double backslash. Can anyone help?
No need to use str.replace or string.replace here, just convert that string to a raw string:
>>> strs = r"C:\Users\Josh\Desktop\20130216"
^
|
notice the 'r'
Below is the repr version of the above string, that's why you're seeing \\ here.
But, in fact the actual string contains just '\' not \\.
>>> strs
'C:\\Users\\Josh\\Desktop\\20130216'
>>> s = r"f\o"
>>> s #repr representation
'f\\o'
>>> len(s) #length is 3, as there's only one `'\'`
3
But when you're going to print this string you'll not get '\\' in the output.
>>> print strs
C:\Users\Josh\Desktop\20130216
If you want the string to show '\\' during print then use str.replace:
>>> new_strs = strs.replace('\\','\\\\')
>>> print new_strs
C:\\Users\\Josh\\Desktop\\20130216
repr version will now show \\\\:
>>> new_strs
'C:\\\\Users\\\\Josh\\\\Desktop\\\\20130216'
Let me make it simple and clear. Lets use the re module in python to escape the special characters.
Python script :
import re
s = "C:\Users\Josh\Desktop"
print s
print re.escape(s)
Output :
C:\Users\Josh\Desktop
C:\\Users\\Josh\\Desktop
Explanation :
Now observe that re.escape function on escaping the special chars in the given string we able to add an other backslash before each backslash, and finally the output results in a double backslash, the desired output.
Hope this helps you.
Use escape characters: "full\\path\\here", "\\" and "\\\\"
In python \ (backslash) is used as an escape character. What this means that in places where you wish to insert a special character (such as newline), you would use the backslash and another character (\n for newline)
With your example string you would notice that when you put "C:\Users\Josh\Desktop\20130216" in the repl you will get "C:\\Users\\Josh\\Desktop\x8130216". This is because \2 has a special meaning in a python string. If you wish to specify \ then you need to put two \\ in your string.
"C:\\Users\\Josh\\Desktop\\28130216"
The other option is to notify python that your entire string must NOT use \ as an escape character by pre-pending the string with r
r"C:\Users\Josh\Desktop\20130216"
This is a "raw" string, and very useful in situations where you need to use lots of backslashes such as with regular expression strings.
In case you still wish to replace that single \ with \\ you would then use:
directory = string.replace(r"C:\Users\Josh\Desktop\20130216", "\\", "\\\\")
Notice that I am not using r' in the last two strings above. This is because, when you use the r' form of strings you cannot end that string with a single \
Why can't Python's raw string literals end with a single backslash?
https://pythonconquerstheuniverse.wordpress.com/2008/06/04/gotcha-%E2%80%94-backslashes-are-escape-characters/
Maybe a syntax error in your case,
you may change the line to:
directory = str(r"C:\Users\Josh\Desktop\20130216").replace('\\','\\\\')
which give you the right following output:
C:\\Users\\Josh\\Desktop\\20130216
The backslash indicates a special escape character. Therefore, directory = path_to_directory.replace("\", "\\") would cause Python to think that the first argument to replace didn't end until the starting quotation of the second argument since it understood the ending quotation as an escape character.
directory=path_to_directory.replace("\\","\\\\")
Given the source string, manipulation with os.path might make more sense, but here's a string solution;
>>> s=r"C:\Users\Josh\Desktop\\20130216"
>>> '\\\\'.join(filter(bool, s.split('\\')))
'C:\\\\Users\\\\Josh\\\\Desktop\\\\20130216'
Note that split treats the \\ in the source string as a delimited empty string. Using filter gets rid of those empty strings so join won't double the already doubled backslashes. Unfortunately, if you have 3 or more, they get reduced to doubled backslashes, but I don't think that hurts you in a windows path expression.
You could use
os.path.abspath(path_with_backlash)
it returns the path with \
Use:
string.replace(r"C:\Users\Josh\Desktop\20130216", "\\", "\\")
Escape the \ character.