[python] Break string into list of characters in Python

Essentially I want to suck a line of text from a file, assign the characters to a list, and create a list of all the separate characters in a list -- a list of lists.

At the moment, I've tried this:

fO = open(filename, 'rU')
fL = fO.readlines()

That's all I've got. I don't quite know how to extract the single characters and assign them to a new list.

The line I get from the file will be something like:

fL = 'FHFF HHXH XXXX HFHX'

I want to turn it into this list, with each single character on its own:

['F', 'H', 'F', 'F', 'H', ...]

You can do this using list:

new_list = list(fL)

Be aware that any spaces in the line will be included in this list, to the best of my knowledge.

Because strings are (immutable) sequences they can be unpacked similar to lists:

with open(filename, 'rU') as fd:
    multiLine = fd.read()
    *lst, = multiLine

When running map(lambda x: x, multiLine) this is clearly more efficient, but in fact it returns a map object instead of a list.

with open(filename, 'rU') as fd:
    multiLine = fd.read()
    list(map(lambda x: x, multiLine))

Turning the map object into a list will take longer than the unpacking method.

a='hello world'
map(lambda x:x, a)

['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']

An easy way is using function “map()”.

fO = open(filename, 'rU')
lst = list(fO.read())

So to add the string hello to a list as individual characters, try this:

newlist = []
newlist[:0] = 'hello'
print (newlist)

  ['h','e','l','l','o']

However, it is easier to do this:

splitlist = list(newlist)
print (splitlist)

python >= 3.5

Version 3.5 onwards allows the use of PEP 448 - Extended Unpacking Generalizations:

>>> string = 'hello'
>>> [*string]
['h', 'e', 'l', 'l', 'o']

This is a specification of the language syntax, so it is faster than calling list:

>>> from timeit import timeit
>>> timeit("list('hello')")
0.3042821969866054
>>> timeit("[*'hello']")
0.1582647830073256

In python many things are iterable including files and strings. Iterating over a filehandler gives you a list of all the lines in that file. Iterating over a string gives you a list of all the characters in that string.

charsFromFile = []
filePath = r'path\to\your\file.txt' #the r before the string lets us use backslashes

for line in open(filePath):
    for char in line:
        charsFromFile.append(char) 
        #apply code on each character here

or if you want a one liner

#the [0] at the end is the line you want to grab.
#the [0] can be removed to grab all lines
[list(a) for a in list(open('test.py'))][0]  

.

.

Edit: as agf mentions you can use itertools.chain.from_iterable

His method is better, unless you want the ability to specify which lines to grab list(itertools.chain.from_iterable(open(filename, 'rU)))

This does however require one to be familiar with itertools, and as a result looses some readablity

If you only want to iterate over the chars, and don't care about storing a list, then I would use the nested for loops. This method is also the most readable.

Or use a fancy list comprehension, which are supposed to be "computationally more efficient", when working with very very large files/lists

fd = open(filename,'r')
chars = [c for line in fd for c in line if c is not " "]
fd.close()

Btw: The answer that was accepted does not account for the whitespaces...

I'm a bit late it seems to be, but...

a='hello'
print list(a)
# ['h','e','l','l', 'o']