How to declare a string as unescaped after storing in a variable?

Question

Continuing from my previous question, this issue is an extension of it.

This issue is somewhat similar to how-do-i-make-a-string-literal-without-having-to-escape-backslashes? but not entirely the same, since I'm thinking of first storing a string in a variable and then declaring that it should be preserved as-is without escaping any escape characters encountered. I just give an example about graph6 strings from graph theory.

s = "ihChWC@?gE_@?@?A_@g?@??C??j?@l??E??Ao??\???m??@I??DF??E`O??GM??@?\
g??S\@o?@g@O??G?w??C?I??D?@o?@g?D???_?M??@??I??D??FK?E_?@Q??G??N??@???\
CPCOaG\a??"

I use the codes from the above link, but it still does not work.

$PreRead = (# /. 
         RowBox@{"RawString", "[", str_String, "]"} | 
           RowBox@{"RawString", "@", str_String} | 
           RowBox@{str_String, "//", "RawString"} :> 
          RowBox@{"StringTrim", "[", ToString@InputForm@str, ",", 
            "\"\\\"\"", "]"}) &;
    s1 = RawString@s
ImportString[s1, "Graph6"]

The code above seems to require the string immediately following RawString, rather than storing the string in a variable. What should I do in this case?

    s1 = RawString@
      "ihChWC@?gE_@?@?A_@g?@??C??j?@l??E??Ao??\???m??@I??DF??E`O??GM??@?\
    g??S\@o?@g@O??G?w??C?I??D?@o?@g?D???_?M??@??I??D??FK?E_?@Q??G??N??@???\
    CPCOaG\a??"
    ImportString[s1, "Graph6"]

I tried to replace the character \ with \\, but it still failed.

s = "ihChWC@?gE_@?@?A_@g?@??C??j?@l??E??Ao??\???m??@I??DF??E`O??GM??@?\
g??S\@o?@g@O??G?w??C?I??D?@o?@g?D???_?M??@??I??D??FK?E_?@Q??G??N??@???\
CPCOaG\a??";
s1 = StringReplace[s, "\\" -> "\\\\"];
ImportString[s1, "Graph6"]

Import::fmterr: Cannot import data as Graph6 format.

I know that in Python, one way to do it is as follows:

import networkx  as nx
escape_dict={'\a':r'\a',
             '\b':r'\b',
             '\c':r'\c',
             '\f':r'\f',
             '\n':r'\n',
             '\r':r'\r',
             '\t':r'\t',
             '\v':r'\v',
             '\'':r'\'',
             '\"':r'\"'}

def raw(text):
    """Returns a raw string representation of text"""
    new_string=''
    for char in text:
        try: 
            new_string += escape_dict[char]
        except KeyError: 
            new_string += char
    return new_string

line = 'ihChWC@?gE_@?@?A_@g?@??C??j?@l??E??Ao??\???m??@I??DF??E`O??GM??@?g??S\@o?@g@O??G?w??C?I??D?@o?@g?D???_?M??@??I??D??FK?E_?@Q??G??N??@???CPCOaG\a??'
line=raw(line)
G = nx.from_graph6_bytes(line.encode())
print(G)

See also how-to-prevent-automatic-escaping-of-special-characters-in-python.

Can Mathematica handle it in a similar way?

Answer 1

There seems to be a bit of a misunderstanding here. A string itself is not escaped or unescaped. A string is just a list of characters.

The issue is with how you transfer these strings between various programs on your computer. In both Mathematica and Python, a string containing a single backslash is written as "\\". There is one character in this:

In[30]:= StringLength["\\"]
Out[30]= 1

In[31]:= ToCharacterCode["\\"]
Out[31]= {92}

But we had to enter it in a special way. It's only an issue of notation.

This special notation means that if you have a text file containing Graph6 code, and you open it with a text editor, you cannot simply copy and paste into a Mathematica notebook or a Python source file. You need to edit all characters that require special notation. For example, if the file contains I]zn\}~nw, you must enter it as I]zn\\}~nw in Mathematica.

Therefore, convenient options are:

Just Import the file instead of copying and pasting.

Or use the notebook where where Mathematica offers to auto-escape for you when pasting into a string. Enter "", position the cursor between the quotes, then paste.

I hit Yes and I get:

Never paste first, quote later. The chance of mistakes is too great. Enter quotes first, paste after, and let Mathematica escape for you automatically.

Answer 2

At least for this particular case, using the UTF8 CharacterEncoding allows you to import the string as "Graph6":

s = "ihChWC@?gE_@?@?A_@g?@??C??j?@l??E??Ao??\???m??@I??DF??E`O??GM??@?\
g??S\@o?@g@O??G?w??C?I??D?@o?@g?D???_?M??@??I??D??FK?E_?@Q??G??N??@???\
CPCOaG\a??"

sUTF8 = ToString[s, CharacterEncoding -> "UTF8"]
g = ImportString[sUTF8, "Graph6"]
(* Output*)