How to put symbols into a list
Question:
How do I put symbols such as , /, :, *, ?, “, <, >, | into a list?
if I do this:
illegalchar = ['', '/' ,':' ,'*', '?', '"', '<', '>', '|']
the commas separating the items will be counted as a string including the ]
PS: It is to check if the filename contains illegal characters (can’t be made into a file), so if there’s any alternative methods, please do tell me, thanks!
Answers:
You need to escape the special characters like
In [2]: something = ["\", "/"]
In [3]: something
Out[3]: ['\', '/']
Printing it will give you the escaped backslash
In [12]: something = ["\", "/"]
In [13]: something
Out[13]: ['\', '/']
In [14]: print ', '.join(something)
, /
Use raw strings (denoted by putting an r in front of your strings). Then, transform your raw string into list:
illegals = [i for i in r'/:*?"<>|']
# OR, using @abccd's suggestion, just use list()
illegals = list(r'/:*?"<>|')
illegals
# ['\', '/', ':', '*', '?', '"', '<', '>', '|']
Note the '\' when printed is still a single backslash, but in value the first backslash is stored as an escape character.
You can read more on the documentation of lexical analysis.
This answers the question, but in reality you a string is treated like a list of characters, so both of the following will return the same elements:
[i for i in list(r'/:*?"<>|')]
[c for c in r'/:*?"<>|']
As for how to identify if a filename has any of these characters, you can do this:
valid_file = 'valid_script.py'
invalid_file = 'invalid?script.py'
validate = lambda f: not any(c for c in r'/:*?"<>|' if c in f)
validate(valid_file)
# True
validate(invalid_file)
# False
This is just one of the many ways. You might even opt for a regex approach:
import re
# Note in regex you still need to escape the slash and backslash in the match group
validate = lambda f: not re.search(r'[\/:*?"<>|]+', f)
validate(valid_file)
# True
validate(invalid_file)
# False
If the idea is just to check for illegal characters, you are doing an overkill here with complex stuffs. python string allow for lookup as they are iterators too. I would go with below easy approach :
In [5]: illegalchar = '/:*?"<>|'
In [6]: if "/" in illegalchar:
print("nay")
...:
nay
downside : one type of quotes have to be skipped which surround the string (' in this case)
Just add the escape character
Change
illegalchar = ['', '/' ,':' ,'*', '?', '"', '<', '>', '|']
to
illegalchar = ['\', '/' ,':' ,'*', '?', '"', '<', '>', '|']
In general I use l = list(r'/:*?"<>|')
However, there are a few sites that do not accept these kind of symbols so I just copied one for a wiki article:
symbols = ['!','#','$','&','(',')','*','+'] => These are the symbols that are accepted on the majority of the platforms
symbols = ['!','#','$','&','(',')','*','+']
How do I put symbols such as , /, :, *, ?, “, <, >, | into a list?
if I do this:
illegalchar = ['', '/' ,':' ,'*', '?', '"', '<', '>', '|']
the commas separating the items will be counted as a string including the ]
PS: It is to check if the filename contains illegal characters (can’t be made into a file), so if there’s any alternative methods, please do tell me, thanks!
You need to escape the special characters like in the string before inserting them into the array, like this:
In [2]: something = ["\", "/"]
In [3]: something
Out[3]: ['\', '/']
Printing it will give you the escaped backslash
In [12]: something = ["\", "/"]
In [13]: something
Out[13]: ['\', '/']
In [14]: print ', '.join(something)
, /
Use raw strings (denoted by putting an r in front of your strings). Then, transform your raw string into list:
illegals = [i for i in r'/:*?"<>|']
# OR, using @abccd's suggestion, just use list()
illegals = list(r'/:*?"<>|')
illegals
# ['\', '/', ':', '*', '?', '"', '<', '>', '|']
Note the '\' when printed is still a single backslash, but in value the first backslash is stored as an escape character.
You can read more on the documentation of lexical analysis.
This answers the question, but in reality you a string is treated like a list of characters, so both of the following will return the same elements:
[i for i in list(r'/:*?"<>|')]
[c for c in r'/:*?"<>|']
As for how to identify if a filename has any of these characters, you can do this:
valid_file = 'valid_script.py'
invalid_file = 'invalid?script.py'
validate = lambda f: not any(c for c in r'/:*?"<>|' if c in f)
validate(valid_file)
# True
validate(invalid_file)
# False
This is just one of the many ways. You might even opt for a regex approach:
import re
# Note in regex you still need to escape the slash and backslash in the match group
validate = lambda f: not re.search(r'[\/:*?"<>|]+', f)
validate(valid_file)
# True
validate(invalid_file)
# False
If the idea is just to check for illegal characters, you are doing an overkill here with complex stuffs. python string allow for lookup as they are iterators too. I would go with below easy approach :
In [5]: illegalchar = '/:*?"<>|'
In [6]: if "/" in illegalchar:
print("nay")
...:
nay
downside : one type of quotes have to be skipped which surround the string (' in this case)
Just add the escape character before the backslash .
Change
illegalchar = ['', '/' ,':' ,'*', '?', '"', '<', '>', '|']
to
illegalchar = ['\', '/' ,':' ,'*', '?', '"', '<', '>', '|']
In general I use l = list(r'/:*?"<>|')
However, there are a few sites that do not accept these kind of symbols so I just copied one for a wiki article:
symbols = ['!','#','$','&','(',')','*','+'] => These are the symbols that are accepted on the majority of the platforms
symbols = ['!','#','$','&','(',')','*','+']