(Python 3.x)Syntax Error EOF while parsing when reading a line from a file.

Question

(Python 3.x)So I keep getting a syntax error when reading a file. I've had this problem for a while now. I've been working on other parts of the program so far(not shown), but can't solve this syntax error. I am very confused. I feel guilty posting about a syntax error but I am out of ideas.

Here is the error: Syntax Error: unexpected EOF while parsing: , line 0, pos 0 @ line 8

Code:

def main(): 
    filename = 'p4input.txt'
    infile = open(filename, "r")
    command = 0
    while command != 3 and command < 3:
        command = eval(infile.readline()) #Problem here 
        convert = eval(infile.readline())
        print(command)

        print(convert)
    print("done")
main()

The input file (p4input.txt) Has the following data:

2
534
1
1101

Complete traceback:
 Traceback (most recent call last):
      File "C:/Users/Ambrin/Desktop/CS 115/TESTER.py", line 16, in <module>
        main()
      File "C:/Users/Ambrin/Desktop/CS 115/TESTER.py", line 8, in <module>
        command = eval(infile.readline())
      File "<string>", line 0, in ?
    Syntax Error: unexpected EOF while parsing: <string>, line 0, pos 0

The syntax error is in the data line from 'p4input.txt' that you are trying to evaluate: you can't evaluate an empty line. eval (and exec) should generally be avoided because they can be a security risk. For details, please see Eval really is dangerous by SO veteran Ned Batchelder. — PM 2Ring
– PM 2Ring, Commented Nov 6, 2017 at 3:27

user8651755 · Accepted Answer · 2017-11-06 03:35:38Z

1

This is happening because when you get to the end of the file, readline() returns an empty string, so you're doing eval(''). You need to check for an empty string and break.

As pointed out in a comment above, you probably shouldn't be using eval. If all your inputs are expected to be integers, you can just use int() instead. You'll still need to check for '' though.

answered Nov 6, 2017 at 3:35

user8651755

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