将文件中的数据添加到列表以进行排序

Question

my text file contains some integer values like below:

100
200
300
400
500
600
700
800
900
1000

i want to add them to a list, then sort them and print the sorted list. i tried something like:

file = open("sample.txt","r")
list1 = []

for line in range(1,11):
    data = file.readline(line)
    list1.append(data)

sortedlist = list1.sort(key=int)
print sortedlist
file.close()

but i got an error like:

Traceback (most recent call last):
  File "o_2.py", line 8, in <module>
    sortedlist = list1.sort(key=int)
ValueError: invalid literal for int() with base 10: ''

also when i checked the list without sorting it was something like:

['1', '00', '\n', '200\n', '300\n', '400\n', '500\n', '600\n', '700\n', '800\n']

i am actually very new to python. so if anybody could explain the whole case with solution it would be very helpful for me. thanks in advance.

Answer 1

You are reading the list wrong; readline does not take the line number, but the maximum number of characters per line :

file.readline([size])

Read one entire line from the file. A trailing newline character is kept in the string (but may be absent when a file ends with an incomplete line). [6] If the size argument is present and non-negative, it is a maximum byte count (including the trailing newline) and an incomplete line may be returned. When size is not 0, an empty string is returned only when EOF is encountered immediately.

Your code would work if you just did file.readline() :

for line in range(1,11):
    data = file.readline()
    list1.append(data)

The current code tries to read only 1, 2 and 3 characters of the first line, which results in '1' , '00' and the '\\n' newline being read separately, followed by max 4 characters of line 2 ( '200\\n' ) etc.

---

However it is not very pythonic either; I would write it as:

with open("sample.txt") as file:
     list1 = [ int(line) for line in file ]

sortedlist = list1.sort()
print sortedlist

with automatically closes the file at the end of indented block. for loop for a file automatically iterates over its lines; [ expression for var in iterable ] is a list comprehension, that is a shorter way of doing:

result = []
for var in iterable:
    result.append(expression)

Or as Jon Clements suggested, if you really want to sort the lines by their numerical value, but keeping them as string:

with open('sample.txt') as file:
    list1 = list(file)  # all lines as a list
    print sorted(list1, key=int)

Answer 2

Your code not removes spaces and newlines.

Import re txt=open('file').read() List=Re.findall('\\d ',txt) now list contain all numbers all other symbols will skipped