读取文件的多种方式？

Question

我不确定在下面第 2 行的两种情况下文件读取方式是否有区别。第一种情况在打开命令中有一个 'r'，第二种情况才不是。两者输出相同的结果。这些只是实现相同结果的不同方法吗？

场景 1：

def readit(filename, astr):
    infile = open(filename, 'r')
    content = infile.read()
    infile.close()
    return content.count(astr)

print(readit("payroll.txt","Sue"))

场景 2：

def readit(filename, astr):
    infile = open(filename)
    content = infile.read()
    infile.close()
    return content.count(astr)

print(readit("payroll.txt","Sue"))

Answer 1

是的，这两段代码是等价的。 'r' 是 open 的默认模式。来自 docs:

open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

mode is an optional string that specifies the mode in which the file is opened. It defaults to 'r' which means open for reading in text mode.

Answer 2

infile = open(filename)    # by default it opens as read-only

没有区别

Answer 3

您可以考虑使用 with 打开文件，除其他好处外，它还可以自动关闭文件。最好逐行计算目标字符串，而不是将整个文件读入内存：

def readit(filename, astr):
    with open(filename) as infile:
        return sum(line.count(astr) for line in infile)

更短，更少内存，更多'Pythonic'

附带说明，line.count(astr) 将计算该子字符串的所有出现次数，即使是较大字符串的一部分。示例：

>>> s='she she he she he sheshe hehe'
>>> s.count('she')
5
>>> s.count('he')
9

考虑拆分文本以获得完整匹配：

>>> [word for word in s.split() if word=='she']
['she', 'she', 'she']
>>> [word for word in s.split() if word=='he']
['he', 'he']

或正则表达式：

>>> re.findall(r'\bshe\b', s)
['she', 'she', 'she']
>>> re.findall(r'\bhe\b', s)
['he', 'he']

Answer 4

来自 python 文档，是一样的。但是如果你想增加可读性，最好添加 'r' 模式 :)

读取文件的多种方式？

Multiple ways to read a file?

python

file