超时时间变量，如果条件为

Question

我有下面的Python代码，它有一个if条件，检查current_ident是否与上一个ident相同，如果相同，则不打印current_ident值

我想做的是在这个检查中添加一个超时，这样只需检查当前和最后一个是否在7秒钟内相同，然后让它打印是否相同。我想可以添加一个全局变量last_read，这样可以节省时间，然后可能使用类似last_read + [timeout] > [current_time]的东西

from nfc import ContactlessFrontend
from time import sleep

ident = '' 

def connected(tag):
    global ident
    current_ident = ''.join('{:02x}'.format(ord(c)) for c in tag.identifier)
    if current_ident != ident:
        print(current_ident)
        ident = current_ident
    return False

clf = ContactlessFrontend('usb')
while True:
    clf.connect(rdwr={'on-connect': connected})
    sleep(1)

Answer 1

您应该能够记录时间以及最后一个标识：

from nfc import ContactlessFrontend
from time import sleep
import time

ident = '' 
next_time = None

def connected(tag):
    global ident
    global next_time
    current_ident = ''.join('{:02x}'.format(ord(c)) for c in tag.identifier)
    if current_ident != ident:
        next_time = time.time() + 7
        print(current_ident)  # Brand new ident
        ident = current_ident
    elif time.time() > next_time:
        next_time = time.time() + 7
        print(current_ident)  # Repeated ident allowed
    # else:  # disallow repeated ident
    return False

clf = ContactlessFrontend('usb')
while True:
    clf.connect(rdwr={'on-connect': connected})
    sleep(1)