If I have:
a = "fwd"
b = "\fwd"
how can I ignore the "\" so something like
print(a in b)
can evaluate to True?
4 Answers
You don't have fwd in b. You have wd, preceded by ASCII codepoint 0C, the FORM FEED character. That's the value Python puts there when you use a \f escape sequence in a regular string literal.
Double the backslash if you want to include a backslash or use a raw string literal:
b = '\\fwd'
b = r'\fwd'
Now a in b works:
>>> 'fwd' in '\\fwd'
True
>>> 'fwd' in r'\fwd'
True
See the String literals documentation:
Unless an
'r'or'R'prefix is present, escape sequences in strings are interpreted according to rules similar to those used by Standard C. The recognized escape sequences are:[...]
\fASCII Formfeed (FF)
answered Apr 14, 2016 at 13:05
Martijn Pieters
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Comments
One way of doing it using raw strings:
>>> a = "fwd"
>>> b = "\fwd"
>>> a in b
False
>>> a = r"fwd"
>>> b = r"\fwd"
>>> a in b
True
The relevant docs
Comments
You need to "escape" the backslash, as in:
b = '\\fwd'
Otherwise, it reads the single backslash + f as an ASCII character (a formfeed).
Here's an example.
>>> a='fwd'
>>> b='\fwd'
>>> c='\\fwd'
>>> a in b
False
>>> a in c
True
Comments
You want to write a letter r to the left of the string as in...
str0 = r"\fwd"
In raw strings, characters are treated literally.
For example, in r"\n" is a black-slash followed by a letter n.
r"\n" does not contain a new-line character.
str1 = r"\n"
\ |
n |
|---|---|
| 92 | 110 |
You can verify this by printing out the underlying numbers with the ordinal function ord().
'\\fwd' [92, 102, 119, 100]
'\\n' [92, 110]
'\n' [10]
'\\n' [92, 110]
Test it yourself:
str0 = r"\fwd"
str1 = r"\n"
str2 = "\n"
str3 = "\\n"
tstrs = [str0, str1, str2, str3]
width = max(len(repr(tstr)) for tstr in tstrs)
for tstr in tstrs:
numbers = list(ord(ch) for ch in tstr)
print(repr(tstr).ljust(4 + width), numbers)
b. There is a form feed character inb, put there by the escape sequence\f.` in the string? Not sure what you mean. Or did you want to actually add a backslash? Then double it (to escape it) or use a raw string literal. I.e.b = '\\fwd'` orb = r'\fwd'.