I am trying to sort the string 'sOrTiNg1234' in the order lowercase-->uppercase-->nums
I did
string = sorted(input(), key = lambda c: (c.isdigit(), c.isupper(),c.islower()))
I had to do the keys as to what seemed right. For example, I first wanted to check if it was a letter or not, and then I wanted to check if it was lower case, and then check if it was uppercase. However, the exact opposite seemed to work.
Could somebody explain how exactly the keys work with sorted?
Thanks a bunch
As briefly hinted in comments, the problem is that True == 1 and False == 0, and thus True is actually sorted after False. So if you put the keys in the "intuitive" order, you get this:
>>> s = 'sOrTiNg1234'
>>> sorted(s, key = lambda c: (c.islower(), c.isupper(), c.isdigit()))
['1', '2', '3', '4', 'O', 'T', 'N', 's', 'r', 'i', 'g']
This might become a bit clearer by having a look at the key tuples:
>>> [(c, map(int, (c.islower(), c.isupper(), c.isdigit()))) for c in s]
[('s', [1, 0, 0]),
('O', [0, 1, 0]),
('r', [1, 0, 0]),
('T', [0, 1, 0]),
('i', [1, 0, 0]),
('N', [0, 1, 0]),
('g', [1, 0, 0]),
('1', [0, 0, 1]),
('2', [0, 0, 1]),
('3', [0, 0, 1]),
('4', [0, 0, 1])]
You can fix this by using the reverse parameter:
>>> sorted(s, key = lambda c: (c.islower(), c.isupper(), c.isdigit()), reverse=True)
['s', 'r', 'i', 'g', 'O', 'T', 'N', '1', '2', '3', '4']
Or, as you did, by reversing the values in the key tuple:
>>> sorted(s, key = lambda c: (c.isdigit(), c.isupper(), c.islower()))
['s', 'r', 'i', 'g', 'O', 'T', 'N', '1', '2', '3', '4']
Or by negating the individual keys (not works, too):
sorted(s, key = lambda c: (-c.islower(), -c.isupper(), -c.isdigit()))
['s', 'r', 'i', 'g', 'O', 'T', 'N', '1', '2', '3', '4']
Also note that using lower and upper is actually redundant:
>>> sorted(s, key = lambda c: (c.isdigit(), c.isupper()))
['s', 'r', 'i', 'g', 'O', 'T', 'N', '1', '2', '3', '4']
And if you also want to sort by the character itself, add it at the end of the tuple:
>>> sorted(s, key = lambda c: (c.isdigit(), c.isupper(), c))
['g', 'i', 'r', 's', 'N', 'O', 'T', '1', '2', '3', '4']
c.islower() is redundant and the expression sorted(s, key = lambda c: (c.isdigit(), c.isupper(), c)) is OKWhat I had done is that I mapped all the alphanumerical characters to somenumbers
The smaller case alphabets are mapped from 0 to 25 by subtracting 97 from the ascii value of smaller case alphabets.
Similarly larger case alphabets are mapped from 26 to 51 by subtracting 65(ord('A')) and adding 26 from the ascii value of smaller case alphabets.
similarly numeric values are mapped from 52 to 61 by subtracting 48(ord('0') from ascii value of numeric characters
Afterr doing all this each character points to somenumber. And all the characters are sorted according to those numbers.And finally after sorting the list I joined all the characters
def function(alpha) :
if alpha.islower():
return ord(alpha)-97 #from a(0) to z(25)
elif alpha.isupper():
return ord(alpha)-65+(26) #from A(26) to Z(51)
else:
return ord(alpha)-48+(52) #from 0(52) to 9(61)
x="sOrTiNg1234"
y=list(x)
y=sorted(y,key=function)
answer=''.join(y)
I hope that it makes sense :)
False < True.True.