Let's say I have a text file containing:
Dan
Warrior
500
1
0
Is there a way I can edit a specific line in that text file? Right now I have this:
#!/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()
Yes, I know that myfile.writelines('Mage')[1]
is incorrect. But you get my point, right? I'm trying to edit line 2 by replacing Warrior with Mage. But can I even do that?
Suppose I have a file named file_name
as following:
this is python
it is file handling
this is editing of line
We have to replace line 2 with "modification is done":
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
I have been practising working on files this evening and realised that I can build on Jochen's answer to provide greater functionality for repeated/multiple use. Unfortunately my answer does not address issue of dealing with large files but does make life easier in smaller files.
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))
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()
And then:
replace_line('stats.txt', 0, 'Mage')
#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)
You can do it in two ways, choose what suits your requirement:
Method I.) Replacing using line number. You can use built-in function enumerate()
in this case:
First, in read mode get all data in a variable
with open("your_file.txt",'r') as f:
get_all=f.readlines()
Second, write to the file (where enumerate comes to action)
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)
Method II.) Using the keyword you want to replace:
Open file in read mode and copy the contents to a list
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.
"Warrior" has been replaced by "Mage", so write the updated data to the file:
with open("some_file.txt","w") as f:
for line in newline:
f.writelines(line)
This is what the output will be in both cases:
Dan Dan
Warrior ------> Mage
500 500
1 1
0 0
This is the easiest way to do this.
fin = open("a.txt")
f = open("file.txt", "wt")
for line in fin:
f.write( line.replace('foo', 'bar') )
fin.close()
f.close()
I hope it will work for you.
If your text contains only one individual:
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()
If your text contains several individuals:
import re
# 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()
If the “job“ of an individual was of a constant length in the texte, you could change only the portion of texte corresponding to the “job“ the desired individual: that’s the same idea as senderle’s one.
But according to me, better would be to put the characteristics of individuals in a dictionnary recorded in file with cPickle:
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
you can use fileinput to do in place editing
import fileinput
for line in fileinput.FileInput("myfile", inplace=1):
if line .....:
print line
Source: Stackoverflow.com