ValueError：以10为底的int（）的无效文字：'2 \\ n3'

Question

I would like to convert my text file below into a list:

4,9,2
3,5,7
8,1,6

Here's my python code so far, but I couldn't understand why it doesn't work:

def main():
file = str(input("Please enter the full name of the desired file (with extension) at the prompt below: \n"))
print (parseCSV(file))

def parseCSV(file):

  file_open = open(file)
  #print (file_open.read())

  with open(file) as f:
    d = f.read().split(',')
    data = list(map(int, d))
    print (data)

main()

The error message is:

line 12, in parseCSV
data = list(map(int, d))
ValueError: invalid literal for int() with base 10: '2\n3'

Thanks :)

Answer 1

Read is reading the entire file (including the newlines). So your actual data looks like:

'4,9,2\n3,5,7\n8,1,6'

You can either read the content in a single line at a time using

d = f.readline().split(',')
while d != "":
    data = list(map(int, d))
    print(data)
    d = f.readline().split(',')

Or, you can handle the new lines ("\\n" and or "\\n\\r") as follows:

d = f.readline().replace("\n", ",").split(',')

Answer 2

With d = f.read().split(',') , you're reading the entire file and splitting on commas. Since the file consists of multiple lines, it will contain newline characters. These characters are not removed by split(',') .

To fix this, iterate over the lines first instead of splitting the whole thing on commas:

d = (item for line in f for item in line.split(','))

Answer 3

f.read() will read everything including the newline character ( \\n ) and so map(int, d) will spit out error.

with open(file) as f:
    for line in f:
        d = line.split(',')
        data = list(map(int, d))
        print (data)

for line in f is a standard way to read a file line by line in python

Answer 4

You need to split by newlines ( '\\n' ), in this case you should use csv library.

>>> import csv
>>> with open('foo.csv') as f:
        print [map(int, row) for row in csv.reader(f)]


[[4, 9, 2], [3, 5, 7], [8, 1, 6]]