无法识别的\\ r \\ n行为

Question

I am using PySerial 3.0.1 and Python3.

Here is my following code.

port.send_break()
while (1):
    sys_reply = port.read(1)
    sys_reply_str = sys_reply.decode('cp437')
    print (sys_reply_str);
    if sys_reply_str == '>':
        break;

and the reply is something like:

...
V
e
r
s
i
o
n
...

>

Which is strange because if I wrote the code like this,

port.send_break()
while (1):
    sys_reply = port.read(100)
    sys_reply_str = sys_reply.decode('cp437')
    print (sys_reply_str);
    if sys_reply_str == '>':
        break;

The result I get is:

...Version...

How is my first code example having a newline every input? There is no "\\n" or "\\r" in the feedback from my sensor at all.

Answer 1

In your first example, you read and print one byte in each loop.
The newline is added by each print .

In the second one, you read the whole sentence at once, as it is shorter than 100 bytes, and print it, so you have only one newline at the end.

You can change the default end of line (\\n) for print with the end parameter, as in:

while (1):
    sys_reply = port.read(1)
    sys_reply_str = sys_reply.decode('cp437')
    print (sys_reply_str, end='');
    if sys_reply_str == '>':
        break;

To answer your comment: the common way to do it is to append each char to a list, and join them into a string at the end. The reason is that strings in Python are immutable, so adding a character at the end (as in s = s + c ) would involve the creation of a new s string at each addition.

received_chars = []
while (1):
    sys_reply = port.read(1)
    sys_reply_str = sys_reply.decode('cp437')
    received_chars.append(sys_reply_str)
    if sys_reply_str == '>':
        break;
received_string = ''.join(received_chars)
print(received_string)