在 Python 中编辑文本文件中的特定行

Question

假设我有一个包含以下内容的文本文件：

Dan
Warrior
500
1
0

有没有办法可以编辑该文本文件中的特定行？现在我有这个：

#!/usr/bin/env python
import io

myfile = open('stats.txt', 'r')
dan = myfile.readline()
print dan
print "Your name: " + dan.split('\n')[0]

try:
    myfile = open('stats.txt', 'a')
    myfile.writelines('Mage')[1]
except IOError:
        myfile.close()
finally:
        myfile.close()

是的，我知道myfile.writelines('Mage')[1] 不正确。但你明白我的意思，对吧？我正在尝试通过用 Mage 替换 Warrior 来编辑第 2 行。但我能做到吗？

Answer 1

你想做这样的事情：

# with is like your try .. finally block in this case
with open('stats.txt', 'r') as file:
    # read a list of lines into data
    data = file.readlines()

print data
print "Your name: " + data[0]

# now change the 2nd line, note that you have to add a newline
data[1] = 'Mage\n'

# and write everything back
with open('stats.txt', 'w') as file:
    file.writelines( data )

这样做的原因是您不能直接在文件中执行“更改第 2 行”之类的操作。您只能覆盖（而不是删除）文件的一部分——这意味着新内容只会覆盖旧内容。因此，如果您在第 2 行上写了“Mage”，则结果行将是“Mageior”。

Answer 2

def replace_line(file_name, line_num, text):
    lines = open(file_name, 'r').readlines()
    lines[line_num] = text
    out = open(file_name, 'w')
    out.writelines(lines)
    out.close()

然后：

replace_line('stats.txt', 0, 'Mage')

Answer 3

您可以使用 fileinput 进行就地编辑

import fileinput
for  line in fileinput.FileInput("myfile", inplace=1):
    if line .....:
         print line

Answer 4

您可以通过两种方式进行操作，选择适合您要求的方式：

方法 I.) 使用行号替换。在这种情况下，您可以使用内置函数enumerate()：

首先，在读取模式获取一个变量中的所有数据

with open("your_file.txt",'r') as f:
    get_all=f.readlines()

其次，写入文件（enumerate 起作用）

with open("your_file.txt",'w') as f:
    for i,line in enumerate(get_all,1):         ## STARTS THE NUMBERING FROM 1 (by default it begins with 0)    
        if i == 2:                              ## OVERWRITES line:2
            f.writelines("Mage\n")
        else:
            f.writelines(line)

方法二。）使用要替换的关键字：

以读取模式打开文件并将内容复制到列表中

with open("some_file.txt","r") as f:
    newline=[]
    for word in f.readlines():        
        newline.append(word.replace("Warrior","Mage"))  ## Replace the keyword while you copy.  

“战士”已被“法师”替换，所以将更新后的数据写入文件：

with open("some_file.txt","w") as f:
    for line in newline:
        f.writelines(line)

这是两种情况下的输出：

Dan                   Dan           
Warrior   ------>     Mage       
500                   500           
1                     1   
0                     0           

Answer 5

如果您的文本只包含一个人：

import re

# creation
with open('pers.txt','wb') as g:
    g.write('Dan \n Warrior \n 500 \r\n 1 \r 0 ')

with open('pers.txt','rb') as h:
    print 'exact content of pers.txt before treatment:\n',repr(h.read())
with open('pers.txt','rU') as h:
    print '\nrU-display of pers.txt before treatment:\n',h.read()


# treatment
def roplo(file_name,what):
    patR = re.compile('^([^\r\n]+[\r\n]+)[^\r\n]+')
    with open(file_name,'rb+') as f:
        ch = f.read()
        f.seek(0)
        f.write(patR.sub('\\1'+what,ch))
roplo('pers.txt','Mage')


# after treatment
with open('pers.txt','rb') as h:
    print '\nexact content of pers.txt after treatment:\n',repr(h.read())
with open('pers.txt','rU') as h:
    print '\nrU-display of pers.txt after treatment:\n',h.read()

如果您的文本包含多个个人：

重新导入

# creation
with open('pers.txt','wb') as g:
    g.write('Dan \n Warrior \n 500 \r\n 1 \r 0 \n Jim  \n  dragonfly\r300\r2\n10\r\nSomo\ncosmonaut\n490\r\n3\r65')

with open('pers.txt','rb') as h:
    print 'exact content of pers.txt before treatment:\n',repr(h.read())
with open('pers.txt','rU') as h:
    print '\nrU-display of pers.txt before treatment:\n',h.read()


# treatment
def ripli(file_name,who,what):
    with open(file_name,'rb+') as f:
        ch = f.read()
        x,y = re.search('^\s*'+who+'\s*[\r\n]+([^\r\n]+)',ch,re.MULTILINE).span(1)
        f.seek(x)
        f.write(what+ch[y:])
ripli('pers.txt','Jim','Wizard')


# after treatment
with open('pers.txt','rb') as h:
    print 'exact content of pers.txt after treatment:\n',repr(h.read())
with open('pers.txt','rU') as h:
    print '\nrU-display of pers.txt after treatment:\n',h.read()

如果个人的“工作”在文本中的长度是恒定的，您可以只更改文本中与所需个人“工作”相对应的部分： 这和 senderle 的想法是一样的。

但在我看来，最好将个人的特征放在一个字典中，用 cPickle 记录在文件中：

from cPickle import dump, load

with open('cards','wb') as f:
    dump({'Dan':['Warrior',500,1,0],'Jim':['dragonfly',300,2,10],'Somo':['cosmonaut',490,3,65]},f)

with open('cards','rb') as g:
    id_cards = load(g)
print 'id_cards before change==',id_cards

id_cards['Jim'][0] = 'Wizard'

with open('cards','w') as h:
    dump(id_cards,h)

with open('cards') as e:
    id_cards = load(e)
print '\nid_cards after change==',id_cards

Answer 6

今晚我一直在练习处理文件，并意识到我可以在 Jochen 的答案的基础上为重复/多次使用提供更大的功能。不幸的是，我的回答并没有解决处理大文件的问题，但确实让小文件的工作更轻松。

with open('filetochange.txt', 'r+') as foo:
    data = foo.readlines()                  #reads file as list
    pos = int(input("Which position in list to edit? "))-1  #list position to edit
    data.insert(pos, "more foo"+"\n")           #inserts before item to edit
    x = data[pos+1]
    data.remove(x)                      #removes item to edit
    foo.seek(0)                     #seeks beginning of file
    for i in data:
        i.strip()                   #strips "\n" from list items
        foo.write(str(i))

Answer 7

写入初始数据，打印一个空的str 以将其更新为新数据 这里我们在代码的最后一行插入一个空的str，这段代码可以用于交互更新，也就是在text.txt文件中追加数据

with open("data.txt", 'w') as f:
    f.write('first line\n'
            'second line\n'
            'third line\n'
            'fourth line\n'
            ' \n')

更新文本文件最后一行的数据

my_file=open('data.txt')
string_list = my_file.readlines()
string_list[-1] = "Edit the list of strings as desired\n"
my_file = open("data.txt", "w")
new_file_contents = "". join(string_list)
my_file. write(new_file_contents)

Answer 8

假设我有一个名为 file_name 的文件，如下所示：

this is python
it is file handling
this is editing of line

我们必须将第 2 行替换为“修改完成”：

f=open("file_name","r+")
a=f.readlines()
for line in f:
   if line.startswith("rai"):
      p=a.index(line)
#so now we have the position of the line which to be modified
a[p]="modification is done"
f.seek(0)
f.truncate() #ersing all data from the file
f.close()
#so now we have an empty file and we will write the modified content now in the file
o=open("file_name","w")
for i in a:
   o.write(i)
o.close()
#now the modification is done in the file

Answer 9

#read file lines and edit specific item

file=open("pythonmydemo.txt",'r')
a=file.readlines()
print(a[0][6:11])

a[0]=a[0][0:5]+' Ericsson\n'
print(a[0])

file=open("pythonmydemo.txt",'w')
file.writelines(a)
file.close()
print(a)

Answer 10

这是最简单的方法。

f = open("file.txt", "wt")
for line in f:
    f.write(line.replace('foo', 'bar'))
f.close()

我希望它对你有用。