Question

我在python编程但是我遇到了一些我无法解决的小问题！问题是，当它在文本文件中打印出来时，它只打印整个输出的一行！否则它有效！我需要帮助才能完成这项工作！

import sys, bz2, string, os
#instead of hardcoding filename, get it from arguments
#filename = os.getcwd()
filename = raw_input("Enter the path of bz2 document e.g. files/access_log-20130301.bz2: ")
print "Using file : " + filename
source_file = bz2.BZ2File(filename, "r") 
for line in source_file:
    #Extract the date and put into a variable 
    logdate = string.split(line)[3][1:12]
    #Extract movie name and put into variable movie
    movie = string.split(line)[6]
    #extract who read the movie username = 
    usernames = string.split(line)[2]
    #Only process the movie line if we have /media/movie in it. 
    if movie.find('media/movies') > 0:
        #Prints all things prosscesed
        print "User:" + usernames + " On:" +  logdate + " Was watching:"+ movie
        #p=open(filename+"record.txt", "w")
        fp=open(filename+"record.txt", "wb+")
        fp.write("User: " + usernames + " On: " +  logdate + " Was watching: "+ movie+" File from:"+filename+"\n")
sys.exit()

Answer 1

问题很可能是每次要编写一行时都打开文件的新文件句柄，而不是先刷新输出。这里有两种可能的解决方案：

在主for循环之前打开要写入的文件。这样，您将只有一个文件句柄，并且缺少刷新不会导致此行为。确保在完成后关闭文件。（考虑使用with块，这将导致文件在块终止时自动关闭：with open(filename + "record.txt", "wb+") as f:）
在fp调用后立即关闭fp.write()，这将强制刷新任何缓冲的输出，至少刷新到内核I / O缓存。

我更喜欢选项1，因为在这种情况下没有理由多次打开和关闭文件。（如果你在文件中写了很多行，这些打开/刷新/关闭周期最终会浪费很多时间！）

选项1看起来像这样：

import sys, bz2, string, os
#instead of hardcoding filename, get it from arguments
#filename = os.getcwd()
filename = raw_input("Enter the path of bz2 document e.g. files/access_log-20130301.bz2: ")
print "Using file : " + filename
with open(filename+"record.txt", "wb+") as fp:
    source_file = bz2.BZ2File(filename, "r") 
    for line in source_file:
        #Extract the date and put into a variable 
        logdate = string.split(line)[3][1:12]
        #Extract movie name and put into variable movie
        movie = string.split(line)[6]
        #extract who read the movie username = 
        usernames = string.split(line)[2]
        #Only process the movie line if we have /media/movie in it. 
        if movie.find('media/movies') > 0:
            #Prints all things prosscesed
            print "User:" + usernames + " On:" +  logdate + " Was watching:"+ movie
            #p=open(filename+"record.txt", "w")
            fp.write("User: " + usernames + " On: " +  logdate + " Was watching: "+ movie+" File from:"+filename+"\n")

# The with block has ended at this point, so the file will already be closed here.

sys.exit()

Answer 2

您正在循环内以写入模式打开输出文件。在主回路之外打开一次。

完成后一定要关闭它。更好的是，写下：

with open(filename + "record.txt", "wb+") as fp:
    for line in source_file:
        ...
        fp.write(...)

以便open上下文管理器随后为您关闭它。

我的代码出了什么问题？蟒蛇

2 个答案: