How to split a string using an empty separator in Python
Question:
What is a good way to do some_string.split('') in python? This syntax gives an error:
a = '1111'
a.split('')
ValueError: empty separator
I would like to obtain:
['1', '1', '1', '1']
Answers:
Use list():
>>> list('1111')
['1', '1', '1', '1']
Alternatively, you can use map() (Python 2.7 only):
>>> map(None, '1111')
['1', '1', '1', '1']
Time differences:
$ python -m timeit "list('1111')"
1000000 loops, best of 3: 0.483 usec per loop
$ python -m timeit "map(None, '1111')"
1000000 loops, best of 3: 0.431 usec per loop
One can cast strings to list directly
>>> list('1111')
['1', '1', '1', '1']
or using list comprehensions
>>> [i for i in '1111']
['1', '1', '1', '1']
second way can be useful if one wants to split strings for substrings more than 1 symbol length
>>> some_string = '12345'
>>> [some_string[i:i+2] for i in range(0, len(some_string), 2)]
['12', '34', '5']
Strings are iterables and can be indexed, hence you don’t really need to split it at all:
>>> for char in '11111':
... print char
...
1
1
1
1
1
>>> '11111'[4]
'1'
You can “split” it with a call to list, but it doesn’t make much difference:
>>> for char in list('11111'):
... print char
...
1
1
1
1
1
>>> list('11111')[4]
'1'
So you only need to do this if your code explicitly expects a list. For example:
>>> list('11111').append('2')
>>> l = list('11111')
>>> l.append(2)
>>> l
['1', '1', '1', '1', '1', 2]
This doesn’t work with a straight string:
>>> l.append('2')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute 'append'
In that case you would need:
>>> l += '2'
>>> l
'111112'
Method #1:
s="Amalraj"
l=[i for i in s]
print(l)
Output:
['A', 'm', 'a', 'l', 'r', 'a', 'j']
Method #2:
s="Amalraj"
l=list(s)
print(l)
Output:
['A', 'm', 'a', 'l', 'r', 'a', 'j']
Method #3:
import re; # importing regular expression module
s="Amalraj"
l=re.findall('.',s)
print(l)
Output:
['A', 'm', 'a', 'l', 'r', 'a', 'j']
If like me you arrived here to split in packets and not char by char, I made this :
>>> n=2
>>> str='423346396677674A446E6838436E304164334A30427874784467567863334942446E41424E413D3D'
>>> [ str[byte:byte+n] for byte in range(0,len(str)) if byte % n == 0 ]
['42', '33', '46', '39', '66', '77', '67', '4A', '44', '6E', '68', '38', '43', '6E', '30', '41', '64', '33', '4A', '30', '42', '78', '74', '78', '44', '67', '56', '78', '63', '33', '49', '42', '44', '6E', '41', '42', '4E', '41', '3D', '3D']
You can even omit the list() call altogether, with a combination of map + lambda fn and then use unpacking.
>>> s = "efgvdfbdb"
>>> [* map(lambda x: x, s) ]
['e', 'f', 'g', 'v', 'd', 'f', 'b', 'd', 'b']
What is a good way to do some_string.split('') in python? This syntax gives an error:
a = '1111'
a.split('')
ValueError: empty separator
I would like to obtain:
['1', '1', '1', '1']
Use list():
>>> list('1111')
['1', '1', '1', '1']
Alternatively, you can use map() (Python 2.7 only):
>>> map(None, '1111')
['1', '1', '1', '1']
Time differences:
$ python -m timeit "list('1111')"
1000000 loops, best of 3: 0.483 usec per loop
$ python -m timeit "map(None, '1111')"
1000000 loops, best of 3: 0.431 usec per loop
One can cast strings to list directly
>>> list('1111')
['1', '1', '1', '1']
or using list comprehensions
>>> [i for i in '1111']
['1', '1', '1', '1']
second way can be useful if one wants to split strings for substrings more than 1 symbol length
>>> some_string = '12345'
>>> [some_string[i:i+2] for i in range(0, len(some_string), 2)]
['12', '34', '5']
Strings are iterables and can be indexed, hence you don’t really need to split it at all:
>>> for char in '11111':
... print char
...
1
1
1
1
1
>>> '11111'[4]
'1'
You can “split” it with a call to list, but it doesn’t make much difference:
>>> for char in list('11111'):
... print char
...
1
1
1
1
1
>>> list('11111')[4]
'1'
So you only need to do this if your code explicitly expects a list. For example:
>>> list('11111').append('2')
>>> l = list('11111')
>>> l.append(2)
>>> l
['1', '1', '1', '1', '1', 2]
This doesn’t work with a straight string:
>>> l.append('2')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute 'append'
In that case you would need:
>>> l += '2'
>>> l
'111112'
Method #1:
s="Amalraj"
l=[i for i in s]
print(l)
Output:
['A', 'm', 'a', 'l', 'r', 'a', 'j']
Method #2:
s="Amalraj"
l=list(s)
print(l)
Output:
['A', 'm', 'a', 'l', 'r', 'a', 'j']
Method #3:
import re; # importing regular expression module
s="Amalraj"
l=re.findall('.',s)
print(l)
Output:
['A', 'm', 'a', 'l', 'r', 'a', 'j']
If like me you arrived here to split in packets and not char by char, I made this :
>>> n=2
>>> str='423346396677674A446E6838436E304164334A30427874784467567863334942446E41424E413D3D'
>>> [ str[byte:byte+n] for byte in range(0,len(str)) if byte % n == 0 ]
['42', '33', '46', '39', '66', '77', '67', '4A', '44', '6E', '68', '38', '43', '6E', '30', '41', '64', '33', '4A', '30', '42', '78', '74', '78', '44', '67', '56', '78', '63', '33', '49', '42', '44', '6E', '41', '42', '4E', '41', '3D', '3D']
You can even omit the list() call altogether, with a combination of map + lambda fn and then use unpacking.
>>> s = "efgvdfbdb"
>>> [* map(lambda x: x, s) ]
['e', 'f', 'g', 'v', 'd', 'f', 'b', 'd', 'b']