This question already has answers here:
Why do backslashes appear twice?
(2 answers)
Closed 7 years ago.
Pretty much as question states- I have a code that finds sentences in a big string using regex- findall(). It then uses this sentence later, however when it uses it it puts a backslash infront of any apostrophe, for example Today's becomes Today\'s. Why is this happening, and how can I stop this happening?
It's called escaping a string. When you use " or ' inside of a string use \ to avoid lexical syntax errors. I believe there is a method that removes the escape character from a string if that's what you'd like to do.
The backslash denotes a so called escape sequence, which basically tells python that this character has to be interpreted differently from a "normal" ' character (which would signal the beginning or end of a string for the interpreter).
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 7 months ago.
I am writing documentations for a python package with a clear_stop_character function, in which users can provide extra stop-chars in a list. In the documentation I have written:
"""
stoplist (list, default empty): Accepts a list of extra stop characters,
should escape special regex characters (e.g., stoplist=['\\*']).
"""
It is crucial for the users to see the double backslash before the stop-char. However, the help() outcome of the built package shows:
"""
stoplist (list, default empty): Accepts a list of extra stop characters,
should escape special regex characters (e.g., stoplist=['\*']).
"""
So, it will be misleading for the users.
BTW, I did not find a solution based on the previous questions.
Any ideas?
\ in Python is an escape character which tells Python to interpret the character following it literally. This means that \\ tells Python to interpret the second \ literally, thus causing the error where the first backslash is not displayed.
The simplest solution to this problem is to use four backslashes: \\\\. This way, Python sees the first backslash and interprets the second one literally, printing \. Then, the third backslash will tell Python to interpret the fourth one literally like \.
Simply rewrite your code as:
"""
stoplist (list, default empty): Accepts a list of extra stop characters,
should escape special regex characters (e.g., stoplist=['\\\\*']).
"""
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 3 years ago.
So I'm trying to write this exact string but I don't \n to make a new line I want to actually print \n on the screen. Any thoughts on how to go about this? (using python
Languages:\npython\nc\njava
adding a backslash will interpret the succeeding backslash character literally. print("\\n").
Either escape the backslash by preceding it with another backslash:
'Languages:\\npython\\nc\\njava'
Or use a raw string by preceding the literal with an r:
r'Languages:\npython\nc\njava'
This question already has answers here:
How to escape “\” characters in python
(4 answers)
Closed 4 years ago.
I am totally confused with the escape characters in Python. Sometimes I expect it to output one single '/', it prints '//'; Sometimes I use '//' as '/' it works, but other times it doesn't; And so on so on...
Some example:
print('\\hello') #output --> \hello
print(['\\hello']) #output --> ['\\hello']
So how should I understand '\hello'， as '\hello' or '\\hello'? Can anyone explain the mechanism of escape characters more generally?
Firstly there is the question of getting the right characters into your strings. Then there is the question of how Python displays your string. The same string can be displayed in two different ways.
>>> s = '\\asd'
>>> s
'\\asd'
>>> print(s)
\asd
In this example the string only has one slash. We use two slashes to create it but that results in a string with one slash. We can see that there's only one slash when we print the string.
But when we display the string simply by typing s we see two slashes. Why is that? In that situation the interpreter shows the repr of the string. That is it shows us the code that would be needed to make the string - we need to use quotes and also two slashes on our code to make a string that then has one slash (as s does).
When you print a list with a string as an element we will see the repr of the string inside the list:
>>> print([s])
['\\asd']
This question already has answers here:
What does the "r" in pythons re.compile(r' pattern flags') mean?
(3 answers)
Closed 5 years ago.
I understand that the 'r' prefix indicates a raw string, hence why in the following example is the 'r' prefix being used, since there are special regex characters in the string, which should not be taken literally?
the 'string' that is being searched is an nltk Text object, I suppose it has something to do with this? However I don't understand how it affects the usage of findall.
moby.findall(r"<a> (<.*>) <man>")
In this particular case, r makes no difference, as this string does not contain any sequences which could be misinterpreted. However, it is a good habit to use r when writing regular expressions, to avoid misinterpretation of sequences like \n or \t; with r, they are treated literally, as two characters - backslash followed by a letter; without r, they evaluate to newline and tab, respectively.
The r preceeding the string is called a sigil.
For example, '\n' will be treated as a newline character, while r'\n' will be treated as the characters \ followed by n.
But for your regex:
moby.findall(r"<a> (<.*>) <man>")
it doesn't make a difference but it is always a good idea to treat regex as raw strings to avoid escaping backslashes.
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.
What is the way for preventing Python from interpreting \ followed by numbers as something else?
e.g.
I get DirectoryNameFromAnotherProgram (say it is equal to 'N:\Some Directory')
print DirectoryNameFromAnotherProgram + '1234.txt'
# prints:
# N:\Some DirectoryS4.txt
Since the string with "\" comes as output from another script, I do not have a choice to change it.
Put a "\" in front of the "\". The meaning of "\" in a sting is: the next character doesn't mean what it normally means. If the next character was not normally special (for example, if it's a digit), it means something special now. If the next character does normally mean something special (for example, a backslash), it's not special now. Either way, the initial "\" has done its thing, and is removed.
Special case: if the next character is not normally special (for example, the "S" in your string), but cannot be made special (the sequence "\S" has no special meaning), then the backslash doesn't do anything and is not removed.