从 python (windows) 中的文本文件中读取行
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Reading lines from text file in python (windows)
提问by feathj
I am working on a simple import routine that translates a text file to a json file format for our system in python.
我正在研究一个简单的导入例程，它将文本文件转换为我们系统的 json 文件格式。
import json
# Open text file for reading
txtFile = open('Boating.Make.txt', 'r')
# Create picklist obj
picklistObj = dict()
picklistObj['name'] = 'Boating.Make'
picklistObj['items'] = list()
i = 0
# Iterate through each make in text file
for line in txtFile:
picklistItemObj = dict()
picklistItemObj['value'] = str(i)
picklistItemObj['text'] = line.strip()
picklistItemObj['selectable'] = True
picklistObj['items'].append(picklistItemObj)
i = i + 1
txtFile.close()
picklistJson = json.dumps(picklistObj, indent=4)
print picklistJson
picklistFile = open('Boating.Make.json', 'w')
picklistFile.write(picklistJson)
picklistFile.close()
My question is, why do I need the "strip"? I thought that python was supposed to magically know the newline constant for whatever environment I am currently in. Am I missing something?
我的问题是，为什么我需要“条”？我认为 python 应该神奇地知道我目前所处的任何环境的换行符常量。我错过了什么吗？
I should clarify that the text file I am reading from is an ASCII file that contains lines of text separated '\r\n'.
我应该澄清一下，我正在读取的文本文件是一个 ASCII 文件，其中包含以 '\r\n' 分隔的文本行。
采纳答案by Eser Aygün
Python keeps the new line characters while enumerating lines. For example, when enumerating a text file such as
Python 在枚举行时保留换行符。例如，在枚举文本文件时，例如
foo
bar
you get two strings: "foo\n"and "bar\n". If you don't want the terminal new line characters, you call strip().
你得到两个字符串："foo\n"和"bar\n"。如果您不想要终端换行符，请调用strip().
I am not a fan of this behavior by the way.
顺便说一下，我不喜欢这种行为。
回答by Akash
See this.
看到这个。
Python is usually built with universal newline support; supplying 'U' opens the file as a text file, but lines may be terminated by any of the following: the Unix end-of-line convention '\n', the Macintosh convention '\r', or the Windows convention '\r\n'
Python 通常内置通用换行支持；提供 'U' 将文件作为文本文件打开，但行可以由以下任何一种终止：Unix 行尾约定 '\n'、Macintosh 约定 '\r' 或 Windows 约定 '\ r\n'
回答by Noctis Skytower
Try the following in a Python interpreter to see what the language does:
在 Python 解释器中尝试以下操作以查看该语言的作用：
open('test1.txt', 'wb').write(b'Hello\nWorld!')
open('test2.txt', 'wb').write(b'Hello\r\nWorld!')
print(list(open('test1.txt'))) # Shows ['Hello\n', 'World!']
print(list(open('test2.txt'))) # Shows ['Hello\n', 'World!']
Python does recognize the correct newlines. Instead of using stripon your strings, you might want to write myString.replace('\n', '')instead. Check the documentation:
Python 确实识别正确的换行符。而不是strip在你的字符串上使用，你可能想改写myString.replace('\n', '')。检查文档：
>>> help(str.strip)
Help on method_descriptor:
strip(...)
S.strip([chars]) -> str
Return a copy of the string S with leading and trailing
whitespace removed.
If chars is given and not None, remove characters in chars instead.
>>> help(str.replace)
Help on method_descriptor:
replace(...)
S.replace(old, new[, count]) -> str
Return a copy of S with all occurrences of substring
old replaced by new. If the optional argument count is
given, only the first count occurrences are replaced.
回答by John Gaines Jr.
You need the strip() because "for line in file:" keeps the line terminators on the lines. It's not explicitly stated in the docs (at least in the 2.71 doc I'm looking at). But it functions in a fashion similar to file.readline(), which does explicitly state that it retains the newline.
您需要 strip() 因为“for line in file:”将行终止符保留在行上。它没有在文档中明确说明（至少在我正在查看的 2.71 文档中）。但它的功能类似于 file.readline()，它明确声明它保留了换行符。
