How to read input from the command line's standard input in Python?

Question

I'd like to separate the input by an blank line, repeat reading the input until 2 blank lines are received. Here is the expected input format:

A
B
C

A B 2
A C 3
C B 4

A B 1

I have tried

for line in sys.stdin:
    node = [line]
    if line == ' ':
        cost = [line.split()]
        if line == ' ':
            distance = [line.split()]

But it can not stop reading input with 2 blank lines. Any advice?

line == ' ' - is line equal to single space character. Are use sure that this is what you need? — user3431635
– user3431635, Commented May 7, 2021 at 6:33

Kuldeep Singh Sidhu · Accepted Answer · 2021-05-07 06:34:47Z

1

This is a very simple loop that stores whatever input you give in lines

when last 2 lines are empty i.e lines[-1]==lines[-2]=="" then break; [just mak sure that you have taken at least 2 inputs from the user so check len(lines)>2]

lines = []
while True:
    inp = input()
    lines.append(inp.strip())
    if len(lines)>2 and lines[-1]==lines[-2]=="":
        break

print('\n'.join(lines))

A
B
C

A B 2
A C 3
C B 4

A B 1

If you don't want to store all the lines

lines = ['temp', 'temp']
while True:
    inp = input()
    lines[-2], lines[-1] = lines[-1], inp.strip() # this changes the second last element by last one and the last one is updated to the new line that is entered
    if lines[-1]==lines[-2]=="":
        break

answered May 7, 2021 at 6:34

Kuldeep Singh Sidhu

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1 Comment

Herman Over a year ago

Thanks, but can I store lines in separate list? I mean I'd like to have a list store everything until reach one blank line, then a second list store the following until reaching one blank line

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