我想在文件中显示行，让用户决定应删除哪一行，然后将所有行写回文件，但用户想要删除的行除外。
这是我到目前为止所尝试的，但我有点卡住了。
def delete_result():
text_file = open('minigolf.txt', 'r')
zork = 0
for line in text_file:
zork = zork + 1
print zork, line
delete_player = raw_input ("Who's result do you want to delete?")
text_file.close()
或
def delete_result():
text_file = open('minigolf.txt', 'r')
for line in text_file:
if ';' in line:
line2 = line.split(";")
print line2
print "***"
delete = raw_input ("Who's result do you want to delete? ")
text_file.close()
minigolf.txt包含：
Sara;37;32;47;
Johan;44;29;34;
Kalle;33;34;34;
Oskar;23;47;45;
答案 0 :(得分：2)
所有其他答案都是有效的，因此您可能通过加载文件，更改内容然后再保存文件来了解如何操作。
我只想指出，有可能直接在存储内存中更改文件的内容。这样做并不总是明智的，事情有它的缺点，但是因为它可能对将来的一些用途有用。
要将内容更改（删除或插入）到现有文件，您可以使用mmap模块。
它允许您映射RAM或存储内存（文件）的一部分，并像访问字符串一样访问和编辑它。或许可以说一个清单。
因此，要删除所需的行，请打开文件，加载其内容并执行find（）或其他内容，以查找要删除的行的索引及其长度。
然后你记忆地映射文件，然后简单地移动你想要向上删除的行的其余内容，因此＆＃34;覆盖＆＃34;不需要的线。你使用切片来做到这一点。然后在移动内容后调整内存映射的大小以切断剩余的字节。因此，您将文件大小调整为正确大小，然后您可以关闭不会关闭文件的mmap。
您可以这种方式将一行插入文件中。您首先调整文件大小，将内容移到最后，以便在您希望显示行的位置创建一个空格，并将其写入。
这听起来有点复杂，而且工作量很大，但实际上并非如此。每次删除行时都可以省去编写整个文件的麻烦。
我没有检查它的速度有多快，而且每次覆盖速度都快。但这是我觉得值得一提的一个解决方案。
以下是一些快速汇编的代码：
# This needs checks and rechecks
# Also, its efficiency is questionable. Some optimization can be done with find() and rfind()
# But we can choose to believe in the module and just do it.
# The nice thing is that we can use find() to point the user, not searching for the line number like mad.
from mmap import mmap
def removeline (fname, nl):
f = open(fname, "rb+")
m = mmap(f.fileno(), 0)
size = m.size()
ixl = 0 # Index of line to delete
nle = 0 # Count new lines found
# Find the line:
while nle!=nl:
# Suppose we know our EOL will always be \n
i = m.find("\n", ixl)
if i==-1: break
ixl = i+1
nle += 1
if ixl>=size: f.close(); return # nl is greater than number of lines in the f
ixle = m.find("\n", ixl) # Index of end of that line
ixle = (ixle+1, None)[ixle==-1] #Either include the EOL in deletion or delete to the EOF
# Line length:
if ixle!=None: ll = ixle-ixl
else:
# Remove from ixl to the end of file.
# I.e. just shrink the file.
ns = size-(size-ixl)
if ns==0:
# Delete all
m.close()
f.close()
f = open(fname, "wb")
f.close()
return
m.resize(ns) # Cut off the rubbish
m.close(); f.close()
return
# Shift the rest over the offending line:
try: m[ixl:size-ll] = m[ixle:size]
except:
m.close()
f.close()
raise
ns = size-ll
if ns==0:
# Delete all - mmap doesn't like to resize to 0 bytes., hm, perhaps f.truncate()
m.close()
f.close()
f = open(fname, "wb")
f.close()
return
m.resize(ns) # Cut off the rubbish
m.close()
f.close()
答案 1 :(得分：1)
line_number = 5 #for example
file = open("foo.txt")
cont = file.read()
cont = cont.splitlines()
cont.pop(line_number-1)
file.close()
file = open("foo.txt", "w")
cont= "\n".join(cont)
file.write(cont)
file.close()
如果你用名字做;试试看：
file = open("foo.txt")
cont = file.read()
cont = cont.splitlines()
line_number = 0
name = "Johan"
for i in cont:
if i.startswith(name):
line_number = cont.index(i)
cont.pop(line_number)
file.close()
file = open("foo.txt", "w")
cont= "\n".join(cont)
file.write(cont)
file.close()
答案 2 :(得分：1)
def delete_result():
with open('minigolf.txt', 'r') as f:
results = f.readlines()
print(results)
user = raw_input('which user do you want to delete')
for res in results:
if user.lower() in res: # assumption that sara == Sara
results.remove(res)
with open('minigolf.txt', 'w') as f:
f.writelines(results)
return 'user was found and removed'
return 'user was not found'
答案 3 :(得分：1)
为了清晰起见，对danidee的回答稍作修改
def delete_result():
with open('minigolf.txt', 'r') as f:
results = f.readlines()
print "\n".join(results)
delete_player = raw_input ("Who's result do you want to delete?")
deleted = False
for res in results:
if delete_player.lower() in res.lower():
results.remove(res)
with open('minigolf.txt', 'w') as f:
f.writelines(results)
print "User was found and removed"
deleted = True
# for
if not deleted:
print "User not found..."
# def
结果：
>> python delete_user.py
Sara;37;32;47;
Johan;44;29;34;
Kalle;33;34;34;
Oskar;23;47;45;
Who's result do you want to delete?sara
User was found and removed
>> cat minigolf.txt
Johan;44;29;34;
Kalle;33;34;34;
Oskar;23;47;45;
>> python delete_user.py
Johan;44;29;34;
Kalle;33;34;34;
Oskar;23;47;45;
Who's result do you want to delete?nonuser
User not found...
答案 4 :(得分：0)
这将解决您的问题并为您提供更强大的处理用户输入的方式：
def delete_result():
with open('minigolf.txt', 'r') as f:
text_file = f.readlines()
# find newline char and strip from endings
if '\r' in text_file[0]:
if '\n' in text_file[0]:
newline = '\r\n'
else:
newline = '\r'
else:
newline = '\n'
text_file = [t[:-len(newline)]
if t[-len(newline):] == newline
else t for t in text_file]
users = set()
for line_number, line in enumerate(text_file):
print line_number + 1, line
users.add(line[:line.index(';')].lower())
# get result from user with exception handling
result = None
while not result:
delete_player = raw_input('Which user do you want to delete? ')
try:
result = str(delete_player).lower()
assert result in users
except ValueError:
print('Sorry, I couldn\'t parse that user.')
except AssertionError:
print('Sorry, I couldn\'t find that user.')
result = None
# write new file
new_file = [t + newline for t in text_file
if t[:t.index(';')].lower() != result]
with open('minigolf.txt', 'w') as f:
f.writelines(new_file)
if __name__ == '__main__':
delete_result()