python 文件阅读列表索引错误：索引超出范围

Question

I run into an error with the following code:

h = 0
num = 0
with open('file1') as f:

    for row in f.readlines():
        line = row.split()

        print(line)

        # check for new
        if int(float(line[0])) != h:
            h = int(float(line[0]))
            num += 1

OUTPUT:

['3', '1', '35', '31.924847576898625', '5.128603105085375', '6.20101', '0.7821899999999999', '0.23388931803044988']
[]
Traceback (most recent call last):
  File "phase_one.py", line 45, in <module>
    if int(float(line[0])) != h:
IndexError: list index out of range

Why is it when I call print(), the actual line is printed, but also there is an empty list '[]' printed after, which is causing this error?

Answer 1

There are two lines in your file. The first line is the first row. The second line of your file is blank. Either

1. remove that line
2. Or, check to see if line is empty before trying to access its first element. Empty lists are falsy, so you can simply do if line and int(line[0])... and short-circuiting will take care of the rest.

line = row.split()
print(line)

if line and int(line[0]) != h:
    h = int(line[0])
    num += 1

3. Or, catch the error that is thrown.

line = row.split()
print(line)

try:
    if int(line[0]) != h:
        h = int(line[0])
        num += 1
except IndexError:
    pass

Also, you don't need to convert the string to float before converting it to int . Simply if int(line[0]):= h: should be sufficient.