python在文本文件中搜索字符串并复制块
我有这个文本文件names.txtpython在文本文件中搜索字符串并复制块,python,file,search,text,copy,Python,File,Search,Text,Copy,我有这个文本文件names.txt Daniel Sam Sameer Code Print Alpha Bravo Charlie 我想搜索字符串“Alpha”并复制行“Alpha”和前面的100行,然后将其写入文件result.txt with open(names.txt) as g: lines = (g.readlines()) for line in lines: if "{0}".format("Alpha") in line:
Daniel
Sam
Sameer
Code
Print
Alpha
Bravo
Charlie
我想搜索字符串“Alpha”并复制行“Alpha”和前面的100行,然后将其写入文件result.txt
with open(names.txt) as g:
lines = (g.readlines())
for line in lines:
if "{0}".format("Alpha") in line:
????????????
我写了这段代码并停在这里,任何人都能帮上忙吗?你需要一个计数器来告诉你哪一行有
Alpha
,这样你就可以返回并得到你需要的前100行了。可能最简单的方法是保存你读过的最后100行的列表,如果当前行是'Alpha'
,则将它们输出到result.txt
文件:
limit = 100
prev_items = []
# Open file and iterate over lines.
with open('names.txt') as f:
for line in f:
# Add the current line to the list.
prev_items.append(line)
# Reduce the list to its newest elements.
prev_items = prev_items[-limit:]
# If the current line is 'Alpha', we don't need to read any more.
if line == 'Alpha':
break
# Append prev_items to the results file.
with open('results.txt', 'a') as f:
f.write('\n'.join(prev_items))
或者,如果您愿意使用除列表
以外的集合,请使用:
您是否遇到了特定的错误?还是你只是在寻求解决方案general@Parker我不知道下一步该做什么,而且我是python新手。我真的不知道下一步该写什么。谢谢,你的代码运行得非常好。还有一件事,你能告诉我需要在代码中更改什么来将100更改为代码中的一个变量吗?@Mohammed:我添加了一个
limit
变量来做你需要的事情-只需相应地调整即可。(我还将prev100
更改为prev_items
,因为它可能不再有100个项目)。
from collections import deque
limit = 100
prev_items = deque(maxlen=limit)
# Open file and iterate over lines.
with open('names.txt') as f:
for line in f:
# Add the line to the deque.
prev_items.append(line)
# If the current line is 'Alpha', we don't need to read any more.
if line == 'Alpha':
break
# Append prev_items to the results file.
with open('results.txt', 'a') as f:
f.write('\n'.join(prev_items))