用Python读/写文件 [英] Reading/writing files in Python

问题描述

我正在尝试从罗素2k中创建一个新的包含股票代号的文本文件，如下所示:

I am trying to create a new text file of stock symbols in the russell 2k from one that looks like this:

我想要的是每行末尾的股票代码.所以我有以下代码:

All I want is the ticker symbol at the end of each line. So I have the following code:

with open("russ.txt", "r") as f:
    for line in f:
        line = line.split()
        line = line[-1]
        if line == "Ticker": continue
        print line
        with open("output.txt", "w") as fh:
            fh.seek(0,2)
            print line
            fh.write(line)

我在output.txt文件中最后得到的只是一行，并且列表中的最后一个股票代号而不是所有股票代号.我认为每次使用fh.seek(0,2)都会在末尾创建新行.我究竟做错了什么?另外，实际上，我不需要创建另一个文档，我可以只编辑当前文档，但是我也无法弄清楚，因此如果您可以向我展示如何只写一个同样可以接受的文件，那么我也可以.

All I end up with in the output.txt file is one line with the very last ticker in the list instead of all the tickers. I thought using fh.seek(0,2) would create a new line at the end each time through. What am I doing wrong? Also, in reality I don't need to create another doc, I could just edit the current one but I couldn't figure that out either so if you could show me how to just write to the same file that also is perfectly acceptable.

推荐答案

文件模式"w"在每个步骤中都会创建一个新的空文件.可以使用模式"a"进行追加，也可以将文件打开的位置移到循环外部.

The filemode "w" creates a new empty file in each step. Either use mode "a" for append, or move the file opening outside the loop.

with open("russ.txt", "r") as f:
    for line in f:
        line = line.split()
        line = line[-1]
        if line == "Ticker": continue
        print line
        with open("output.txt", "a") as fh:
            fh.write(line + "\n")

或者更好，只打开一次文件:

or better, open the file only once:

with open("russ.txt", "r") as f, open("output.txt", "w") as fh:
    for line in f:
        symbol = line.split()[-1]
        if symbol != "Ticker":
            print symbol
            fh.write(symbol + "\n")

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