I have a text document that contains a list of numbers and I want to convert it to a list. Right now I can only get the entire list in the 0th entry of the list, but I want each number to be an element of a list. Does anyone know of an easy way to do this in Python?
1000
2000
3000
4000
to
['1000','2000','3000','4000']
To convert a Python string into a list use the str.split method:
>>> '1000 2000 3000 4000'.split()
['1000', '2000', '3000', '4000']
split has some options: look them up for advanced uses.
You can also read the file into a list with the readlines() method of a file object - it returns a list of lines. For example, to get a list of integers from that file, you can do:
lst = map(int, open('filename.txt').readlines())
P.S: See some other methods for doing the same in the comments. Some of those methods are nicer (more Pythonic) than mine
str.split, not string.split, the latter is obsolete anyway.
readlines method. For example, you could get the same results as your last snippet with map(int, open('filename.txt')).
map built-in function plus if the file is big enough iteration over file will be faster and more memory efficient than readlines: lst = [int(line) for line in open('filename.txt')]
lst = [int(line) for line in open('filename.txt')] is much better (and more efficient) idiomatic Python for your second example. chuckle I should read the other comments before I post one.
with open('filename.txt') as f: lst = map(int, f.readlines()) $ cat > t.txt
1
2
3
4
^D
$ python
Python 2.6.1 (r261:67515, Jul 7 2009, 23:51:51)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> l = [l.strip() for l in open('t.txt')]
>>> l
['1', '2', '3', '4']
>>>
>>> open("myfile.txt").readlines()
>>> lines = open("myfile.txt").readlines()
>>> lines
['1000\n', '2000\n', '3000\n', '4000\n']
>>> clean_lines = [x.strip() for x in lines]
>>> clean_lines
['1000', '2000', '3000', '4000']
Or, if you have a string already, use str.split:
>>> myfile
'1000\n2000\n3000\n4000\n'
>>> myfile.splitlines()
['1000', '2000', '3000', '4000', '']
You can remove the empty element with a list comprehension (or just a regular for loop)
>>> [x for x in myfile.splitlines() if x != ""]
['1000', '2000', '3000', '4000']
s.splitlines(), not s.split("\n") with open('file.txt', 'rb') as f:
data = f.read()
lines = [s.strip() for s in data.split('\n') if s]
You can achieve this using the splitlines() method in python
data = """1000
2000
3000
4000"""
number_list = data.splitlines()
You might need to strip newlines.
# list of strings
[number for number in open("file.txt")]
# list of integers
[int(number) for number in open("file.txt")]
list builtin instead of a list comprehension - list(open("myfile.txt")) -> ['1000\n', '2000\n', '3000\n', '4000\n']list(open("myfile")) is the same as open("myfile").readlines() - by default iterating over a file with use the readlines methodIf you already have a list that has been converted to a string by the str() method--like str(my_list)-- I have found that the easiest way to convert it back into a list is just to use eval(file_contents).
['1000','2000','3000','4000']? Maybe[1000,2000,3000,4000]would be better?