Python沒有每秒運行

Question

import threading
import time

def cold_temp():
    # Open the file that we viewed earlier so that python can see what is in it. Replace the serial number as before. 
    tfile = open("/sys/bus/w1/devices/28-021571bf69ff/w1_slave") 
    # Read all of the text in the file. 
    text = tfile.read() 
    # Close the file now that the text has been read. 
    tfile.close() 
    # Split the text with new lines (\n) and select the second line. 
    secondline = text.split("\n")[1] 
    # Split the line into words, referring to the spaces, and select the 10th word (counting from 0). 
    temperaturedata = secondline.split(" ")[9] 
    # The first two characters are "t=", so get rid of those and convert the temperature from a string to a number. 
    temperature = float(temperaturedata[2:]) 
    # Put the decimal point in the right place and display it. 
    temperature = temperature / 1000 
    return temperature

output = cold_temp()    
f = open('/var/www/html/coldtemp.html', 'w')
print >> f, output
f.close()
cold_temp()

我已經嘗試了上面的和一個簡單的

def cold_temp():
    while True:
        # Open the file that we viewed earlier so that python can see what is in it. Replace the serial number as before. 
        tfile = open("/sys/bus/w1/devices/28-021571bf69ff/w1_slave") 
        # Read all of the text in the file. 
        text = tfile.read() 
        # Close the file now that the text has been read. 
        tfile.close() 
        # Split the text with new lines (\n) and select the second line. 
        secondline = text.split("\n")[1] 
        # Split the line into words, referring to the spaces, and select the 10th word (counting from 0). 
        temperaturedata = secondline.split(" ")[9] 
        # The first two characters are "t=", so get rid of those and convert the temperature from a string to a number. 
        temperature = float(temperaturedata[2:]) 
        # Put the decimal point in the right place and display it. 
        temperature = temperature / 1000 
        return temperature

        output = cold_temp()    
        f = open('/var/www/html/coldtemp.html', 'w')
        print >> f, output
        f.close()
        time.sleep(1)

我想每秒運行一次腳本。 以上兩種運行一次，然后結束。

Answer 1

您可以使用sched模塊來安排某些內容重復運行，無論是每兩個小時還是每秒一次。

如果您的函數運行時間超過一秒（不太可能僅用於檢查溫​​度），則會有延遲。

由於重復執行功能需要花費時間，因此您還會看到一些“漂移”。 您的函數運行所花費的所有微小的“時間”最終都會累加起來。

例如-

import sched, time

s = sched.scheduler(time.time, time.sleep)
def some_function():

    print time.time()
    s.enter(1, 0, some_function)

s.enter(1, 0, some_function)
s.run()

Answer 2

您的while循環在錯誤的位置。 我隨意更改代碼以使用with子句，這是打開文件的更標准的方法，但是如果您使用的是真正的python，它將被破壞。

import threading
import time

def cold_temp():
    # Open the file that we viewed earlier so that python can see what is in it. Replace the serial number as before. 
    with open("/sys/bus/w1/devices/28-021571bf69ff/w1_slave") as tfile:
        # skip first line, keep second line
        next(tfile)
        secondline = next(tfile)
    # Split the line into words, referring to the spaces, and select the 10th word (counting from 0). 
    temperaturedata = secondline.split(" ")[9] 
    # The first two characters are "t=", so get rid of those and convert the temperature from a string to a number. 
    temperature = float(temperaturedata[2:]) 
    # Put the decimal point in the right place and display it. 
    temperature = temperature / 1000 
    return temperature

while True:
    output = cold_temp()    
    with open('/var/www/html/coldtemp.html', 'w') as f:
        print >> f, output
    time.sleep(1)

Answer 3

第一個運行一次，因為您沒有給它任何重復運行的方式。 第二個return一個return ，該return在函數甚至沒有輸出任何內容之前就退出了該函數（並因此退出了循環）。 刪除return ，僅將temperature用作output值。