python replace single backslash with double backsl

问题:

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?

回答1:

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'

回答2:

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.

回答3:

Use escape characters: "full\\path\\here", "\\" and "\\\\"

回答4:

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 sting 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 sting. 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 sting must NOT use \ as an escape character by pre-pending the sting 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 stings.

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 stings above. This is because, when you use the r' form of stings 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/

回答5:

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

回答6:

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.

回答7:

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("\\","\\\\")

回答8:

You could use

os.path.abspath(path_with_backlash)

it returns the path with \

回答9:

Use:

string.replace(r"C:\Users\Josh\Desktop\20130216", "\\", "\\")

Escape the \ character.