我正在研究如何在 Python 中进行文件输入和输出。我编写了以下代码,以将文件中的名称列表(每行一个)读取到另一个文件中,同时根据文件中的名称检查名称并将文本附加到文件中的出现处。该代码有效。能不能做得更好?
我想对输入和输出文件使用 with open(...
语句,但看不到它们如何位于同一个 block 中,这意味着我需要存储临时位置的名称。
def filter(txt, oldfile, newfile):
'''\
Read a list of names from a file line by line into an output file.
If a line begins with a particular name, insert a string of text
after the name before appending the line to the output file.
'''
outfile = open(newfile, 'w')
with open(oldfile, 'r', encoding='utf-8') as infile:
for line in infile:
if line.startswith(txt):
line = line[0:len(txt)] + ' - Truly a great person!\n'
outfile.write(line)
outfile.close()
return # Do I gain anything by including this?
# input the name you want to check against
text = input('Please enter the name of a great person: ')
letsgo = filter(text,'Spanish', 'Spanish2')
最佳答案
Python 允许将多个 open()
语句放在一个 with
中。你用逗号分隔它们。您的代码将是:
def filter(txt, oldfile, newfile):
'''\
Read a list of names from a file line by line into an output file.
If a line begins with a particular name, insert a string of text
after the name before appending the line to the output file.
'''
with open(newfile, 'w') as outfile, open(oldfile, 'r', encoding='utf-8') as infile:
for line in infile:
if line.startswith(txt):
line = line[0:len(txt)] + ' - Truly a great person!\n'
outfile.write(line)
# input the name you want to check against
text = input('Please enter the name of a great person: ')
letsgo = filter(text,'Spanish', 'Spanish2')
不,通过在函数末尾放置显式 return
不会获得任何好处。你可以使用 return
提前退出,但你最后有它,没有它,函数将退出。 (当然对于返回值的函数,您可以使用 return
来指定要返回的值。)
在引入 with
语句时,Python 2.5 或在 Python 2.6 中不支持将多个 open()
项与 with
一起使用,但它在 Python 2.7 和 Python 3.1 或更高版本中受支持。
http://docs.python.org/reference/compound_stmts.html#the-with-statement http://docs.python.org/release/3.1/reference/compound_stmts.html#the-with-statement
如果您正在编写必须在 Python 2.5、2.6 或 3.0 中运行的代码,请将 with
语句嵌套为建议的其他答案或使用 contextlib.nested
.
https://stackoverflow.com/questions/9282967/