如何使用python从文件中仅读取数字以列为整数

Question

I have a txt file like this:

input 0 1 2 3 4 5 6 7 0
output 127 191 223 239 247 251 253 254 0

I want to read integers 0 1 2 3 4 5 6 7 0 to a list. Here is my code:

f=open('data.txt','r')
for line in f:
        if 'input' in line:
                linestr=line.strip('input')
                #linestr=list(map(int,linestr)
                print(linestr)

The output is

0 1 2 3 4 5 6 7 0

But when i add "print(linestr[0]+1)" , it shows error "TypeError: must be str, not int" Is that means the list I got is still not integer? How can I use the number as int in this list? Thx all

Answer 1

It is still a string. Test this by type(linestr) . You cannot add an integer to a string.

What you need to do is extract each value from liststr . This can be done easily using strip() and running through this list to get each value, next you need to pass it to int() to turn each value into an integer, append it to your list with integers, then you can use it as expected:

new_liststr = []
for i in liststr.split():
    new_liststr.append(int(i))

print(new_linestr[0]+1)

Or as a single liner:

new_liststr = [int(i) for i in liststr.split()] 
print(new_linestr[0]+1)

Answer 2

You can not att a str and an int inside a print()

print(linestr[0]+1)
                 ^
                 |
             not a str

You can:

print(int(linestr[0])+1)

Answer 3

from pathlib import Path
doc="""input 0 1 2 3 4 5 6 7 0
output 127 191 223 239 247 251 253 254 0"""
Path('temp.txt').write_text(doc)

with open('temp.txt','r') as f:
    for line in f:
        if 'input' in line:
             linestr=line.strip('input')

# here is what you have accomplished:
assert linestr == ' 0 1 2 3 4 5 6 7 0\n'
assert linestr == ' '
#you are tying to do ' '+1

linelist = map(int, linestr.strip().split(' '))
assert linestr[0]+1 == 1

PS your original import is a terrible workaround, please learn to use https://docs.python.org/3/library/csv.html

Answer 4

output = []
with open('data.txt','r') as f:
    for line in f:
        l = line.split()
        if l[0] == 'input':
            output.extend(map(int, l[1:]))