python - 当我只需要向用户添加的行时，为什么它会在 nlist 中记录额外的项目/行( ' ' )？

Question

示例:我输入正数:1、2、3、4，然后输入 -1 结束第一个函数。第二个函数中显示的列表(nlist)为['1', '2', '3', '4', '']。这个额外的第五项从哪里来？我该如何防止它？

def pos_num():

    # Open num.txt and define num
    num_list = open('num.txt', 'w')
    num = 1

    # While num is positive, ask user for input
    while num >= 0:
        num = int(input('Type + number to add to num_list, - number to end: '))

        # If user input is positive: \
        # convert to str, add to list, convert to int to continue loop
        if num >= 0:
            num = str(num)
            num_list.write(num + '\n')
            num = int(num)

        # If user input is negative: \
        # close num.txt and inform user
        else:
            num_list.close()
            print('List has been written to num.txt')

# Call program 1
pos_num()

# Program 2: Number File Reader
def nfread():

    # Ask user for filename to open
    filename = input('Filename: ')
    infile = open(filename, 'r')

    # Create empty list
    nlist = []

    # Read first line, strip '\n', append to nlist, begin line count
    line = infile.readline()
    line = line.rstrip('\n')
    nlist.append(line)
    count = 1

    # While line is not empty: \
    # read line, strip '\n', append line to nlist, add 1 to count
    while line != '':
        line = infile.readline()
        line = line.rstrip('\n')
        nlist.append(line)
        count += 1
        print(line, count)

    # Close num.txt
    infile.close()

    # Return nlist
    return nlist

Answer 1

考虑更改此 block :

# Read first line, strip '\n', append to nlist, begin line count
line = infile.readline()
line = line.rstrip('\n')
nlist.append(line)
count = 1

# While line is not empty: \
# read line, strip '\n', append line to nlist, add 1 to count
while line != '':
    line = infile.readline()
    line = line.rstrip('\n')
    nlist.append(line)
    count += 1
    print(line, count)

类似的事情

count = 0
for line in infile:
    line = line.rstrip()
    if line:
        nlist.append(line)
        count += 1
        print(line, count)

在所有更改中，应该修复您的程序的更改是添加 if line: ——它将导致您的程序不向您的程序附加一个空元素。列表(仅对换行符调用 .rstrip() 的结果)。