Python（3）readline返回空字符串，无论文件中有什么

Question

我有一个Python（3）程序，该程序从文件中读取一些数据，获取相关部分，然后将其吐到其他地方。 问题在于file.readline()已开始拒绝从任何文件获取任何行。 它只是返回一个空字符串，就像它在文件末尾一样。 文件不是问题，我使用快速脚本进行了检查（读取文件，逐行打印）。 可能的解决方案（尽管我不知道为什么）是我使用2to3将代码转换为python3，但查看它打印的差异，我看不到对文件I / O的任何修改。

这是程序：

import threading
import time

def runFile(eventFile, channelRefFileName, serialPorts, timeScale, maxPEs):
    timer0 = threading.Timer(.0001, turnOffLED, [0, 0, 0, 1])
    numEvents = getNumEvents(eventFile)
    eventCount = 0
    while 1:
        linein = eventFile.readline()
        #if linein == '' or '\n' or '\r\n' or '\r': break
        #above checks if the end of file has been reached, below is debugging
        if linein == '': print('EOF')
        if linein == '\n': print('linefeed')
        if linein == '\r\n': print('carrige return/ linefeed')
        if linein == '\r' : print('carrige return')
        if linein == 'New Event\n': 
            print('New Event', eventCount, ': file is', 
            (eventCount/numEvents)*100, '% done.')
            eventCount += 1
            #insert event sleep time here
            continue
         linein = linein.split(' ')
         del(linein[::2])
         linein[2] = linein[2][:-1]
         linein[1] = float(linein[1])
         if linein[1] < 0: linein[1] = linein[1] * (-1)
         channel = channelLookup(linein[0], channelRefFileName)
         #serialPorts[channel[0]].write(str(channel[1],linein[2]))
         if timer0.isAlive:
            #use backup timer
            timer1 = threading.Timer(0.005, turnOffLED, [serialPorts, channel[0], channel[1], 0])           
        timer1.start()
    else:
        #use primary timer
        timer0 = threading.Timer(0.005, turnOffLED, [serialPorts, channel[0], channel[1], 0])
        timer0.start()
    print('Sleeping:', linein[1]*timeScale)
    time.sleep(linein[1]*timeScale)

def channelLookup(channel, channelRefFile):
    channelRef = open(channelRefFile, 'r')
    for line in channelRef:
        if channel in line:
            linein = line
            break
    linein = linein.split('-')
    channelRef.close()
    return linein[1:]

def turnOffLED(serialPorts, arduino, pmt, bs):
    if bs: return -1
    #serialPorts[arduino].write(str(pmt,0))

def getNumEvents(eventFile):
    i = 0
    for lines in eventFile:
        if lines == 'New Event\n':
            i += 1
   return i

上面是由：

import hawc
import datetime

timeScale = 0.001 
#timeScale of 0.000001 results in runtime of 0:06:52.858136
#a timeScale of 0.001 is 9:28:34.837992
eventSleep = 0
maxPEs = 1000
serialPorts = [0, 1, 2, 3, 4]
channelRefFileName = 'Data/hawc-arduino_channel_lookup'
st = datetime.datetime.now()
print('Start time is', st)

eventFile = open('Data/events.txt', 'r')
hawc.runFile(eventFile, channelRefFileName, serialPorts, timeScale, maxPEs)

eventFile.close()

et = datetime.datetime.now()
print('End time is', et)
print('File has run for', et-st)
print('--------Done---------')

这是程序可能处理的一些示例数据（一个文件可能约500000行）：

Channel: 447 Time: 121.263 PEs: 2263.38
Channel: 445 Time: 118.556 PEs: 1176.54
Channel: 448 Time: 120.384 PEs: 1159.59
Channel: 446 Time: 122.798 PEs: 983.949
Channel: 499 Time: 129.983 PEs: 762.07

Answer 1

getNumEvents占用整个文件，因此当您四处阅读时，其指针已经在末尾。 而是使用seek重置文件指针，如下所示：

def runFile(eventFile, channelRefFileName, serialPorts, timeScale, maxPEs):
    timer0 = threading.Timer(.0001, turnOffLED, [0, 0, 0, 1])
    numEvents = getNumEvents(eventFile)
    eventFile.seek(0, 0)
    eventCount = 0
    for linein in eventFile:
        if linein == '': print('EOF')
        ....