I have two files in a directory. I'd like to read the lines from each of the files. Unfortunately when I try to do so with the following code, there is no output.
from pathlib import Path
p = Path('tmp')
for file in p.iterdir():
print(file.name)
functions.py
test.txt
for file in p.iterdir():
f = open(file, 'r')
f.readlines()
You're reading all the lines from the file, but you're not outputting them. If you want to print the lines to standard output, you need to use print() as you did in your first example.
You can also write this somewhat more elegantly using contexts and more iterators:
from pathlib import Path
file = Path('test.txt')
with file.open() as open_file:
for line in open_file:
print(line, end="")
test.txt:
Spam
Spam
Spam
Wonderful
Spam!
Spamity
Spam
Result:
Spam
Spam
Spam
Wonderful
Spam!
Spamity
Spam
Using a context for opening the file (with file.open()) means you inherently set up closing the file, and the iterator for the lines (for line in open_file) means you're not loading the whole file at once (an important consideration with larger files).
Setting end="" in print() is optional depending on how your source files are structured, as you might otherwise end up printing extra blank lines in your output.
You could use fileinput:
import os
import fileinput
for line in fileinput.input(os.listdir('.')):
print(line)
You should print data like this from text.py
count = 1
f = open(file, 'r')
Lines = f.readlines()
for line in Lines:
count += 1
print("Line {}: {}".format(count, line.strip()))
Output will look like:
Line 1: ...
Line 2: ...
Line 3: ...
you can see reading line example here - Line reading
I have file looking like this:
face LODRxERROR
{
source R/com/int/LRxAMEexception.csv
contains R/saqf/LAWODRxERROR.ddf
contains R/bld/LAWODRxERRORtyp.h
contains R/bld/LAWODRxERRORtyp.hpp
requires LAWODRxERR
}
At the moment I'm able to read a specific line and store it. But I need to be more specific. Instead of reading the whole line. I would like to read only the file name no the directory. So, instead of reading R/bld/LAWODRxERRORtyp.hpp I would like to read only LAWODRxERRORtyp.hpp
Here is my python code so far:
with open(file) as scope:
for line in scope:
line = line.strip()
if line.startswith('contains') and line.endswith('.h') or line.endswith('.hpp'):
scopeFileList.append(line.split()[-1])
Thanks in advance
You can use the built-in function os.path.basename() to get only the file-name from a path:
from os.path import basename
with open(file) as scope:
for line in scope:
line = line.strip()
if line.startswith('contains') and line.endswith('.h') or line.endswith('.hpp'):
path = line.split()[-1]
scopeFileList.append(basename(path))
Try this,
with open("file1.txt", "r") as f:
data = [line.replace("\n","").split('/')[-1] for line in f.readlines() if '.' in line]
Output:
print(data)
['LRxAMEexception.csv',
'LAWODRxERROR.ddf',
'LAWODRxERRORtyp.h',
'LAWODRxERRORtyp.hpp']
Try this: You can use the re.search to find the file names from a path
with open('new_file.txt') as file:
for line in file:
line = line.strip()
if line.startswith('source') or line.startswith('contains'):
file_names = re.search('/(.+?)\/((\w+)\.\w+$\Z)', line).group(2)
print(file_names)
O/P:
'LRxAMEexception.csv'
'LAWODRxERROR.ddf'
'LAWODRxERRORtyp.h'
'LAWODRxERRORtyp.hpp'
I want to loop over the contents of a text file and do a search and replace on some lines and write the result back to the file. I could first load the whole file in memory and then write it back, but that probably is not the best way to do it.
What is the best way to do this, within the following code?
f = open(file)
for line in f:
if line.contains('foo'):
newline = line.replace('foo', 'bar')
# how to write this newline back to the file
The shortest way would probably be to use the fileinput module. For example, the following adds line numbers to a file, in-place:
import fileinput
for line in fileinput.input("test.txt", inplace=True):
print('{} {}'.format(fileinput.filelineno(), line), end='') # for Python 3
# print "%d: %s" % (fileinput.filelineno(), line), # for Python 2
What happens here is:
The original file is moved to a backup file
The standard output is redirected to the original file within the loop
Thus any print statements write back into the original file
fileinput has more bells and whistles. For example, it can be used to automatically operate on all files in sys.args[1:], without your having to iterate over them explicitly. Starting with Python 3.2 it also provides a convenient context manager for use in a with statement.
While fileinput is great for throwaway scripts, I would be wary of using it in real code because admittedly it's not very readable or familiar. In real (production) code it's worthwhile to spend just a few more lines of code to make the process explicit and thus make the code readable.
There are two options:
The file is not overly large, and you can just read it wholly to memory. Then close the file, reopen it in writing mode and write the modified contents back.
The file is too large to be stored in memory; you can move it over to a temporary file and open that, reading it line by line, writing back into the original file. Note that this requires twice the storage.
I guess something like this should do it. It basically writes the content to a new file and replaces the old file with the new file:
from tempfile import mkstemp
from shutil import move, copymode
from os import fdopen, remove
def replace(file_path, pattern, subst):
#Create temp file
fh, abs_path = mkstemp()
with fdopen(fh,'w') as new_file:
with open(file_path) as old_file:
for line in old_file:
new_file.write(line.replace(pattern, subst))
#Copy the file permissions from the old file to the new file
copymode(file_path, abs_path)
#Remove original file
remove(file_path)
#Move new file
move(abs_path, file_path)
Here's another example that was tested, and will match search & replace patterns:
import fileinput
import sys
def replaceAll(file,searchExp,replaceExp):
for line in fileinput.input(file, inplace=1):
if searchExp in line:
line = line.replace(searchExp,replaceExp)
sys.stdout.write(line)
Example use:
replaceAll("/fooBar.txt","Hello\sWorld!$","Goodbye\sWorld.")
This should work: (inplace editing)
import fileinput
# Does a list of files, and
# redirects STDOUT to the file in question
for line in fileinput.input(files, inplace = 1):
print line.replace("foo", "bar"),
Based on the answer by Thomas Watnedal.
However, this does not answer the line-to-line part of the original question exactly. The function can still replace on a line-to-line basis
This implementation replaces the file contents without using temporary files, as a consequence file permissions remain unchanged.
Also re.sub instead of replace, allows regex replacement instead of plain text replacement only.
Reading the file as a single string instead of line by line allows for multiline match and replacement.
import re
def replace(file, pattern, subst):
# Read contents from file as a single string
file_handle = open(file, 'r')
file_string = file_handle.read()
file_handle.close()
# Use RE package to allow for replacement (also allowing for (multiline) REGEX)
file_string = (re.sub(pattern, subst, file_string))
# Write contents to file.
# Using mode 'w' truncates the file.
file_handle = open(file, 'w')
file_handle.write(file_string)
file_handle.close()
As lassevk suggests, write out the new file as you go, here is some example code:
fin = open("a.txt")
fout = open("b.txt", "wt")
for line in fin:
fout.write( line.replace('foo', 'bar') )
fin.close()
fout.close()
If you're wanting a generic function that replaces any text with some other text, this is likely the best way to go, particularly if you're a fan of regex's:
import re
def replace( filePath, text, subs, flags=0 ):
with open( filePath, "r+" ) as file:
fileContents = file.read()
textPattern = re.compile( re.escape( text ), flags )
fileContents = textPattern.sub( subs, fileContents )
file.seek( 0 )
file.truncate()
file.write( fileContents )
A more pythonic way would be to use context managers like the code below:
from tempfile import mkstemp
from shutil import move
from os import remove
def replace(source_file_path, pattern, substring):
fh, target_file_path = mkstemp()
with open(target_file_path, 'w') as target_file:
with open(source_file_path, 'r') as source_file:
for line in source_file:
target_file.write(line.replace(pattern, substring))
remove(source_file_path)
move(target_file_path, source_file_path)
You can find the full snippet here.
fileinput is quite straightforward as mentioned on previous answers:
import fileinput
def replace_in_file(file_path, search_text, new_text):
with fileinput.input(file_path, inplace=True) as file:
for line in file:
new_line = line.replace(search_text, new_text)
print(new_line, end='')
Explanation:
fileinput can accept multiple files, but I prefer to close each single file as soon as it is being processed. So placed single file_path in with statement.
print statement does not print anything when inplace=True, because STDOUT is being forwarded to the original file.
end='' in print statement is to eliminate intermediate blank new lines.
You can used it as follows:
file_path = '/path/to/my/file'
replace_in_file(file_path, 'old-text', 'new-text')
Create a new file, copy lines from the old to the new, and do the replacing before you write the lines to the new file.
Expanding on #Kiran's answer, which I agree is more succinct and Pythonic, this adds codecs to support the reading and writing of UTF-8:
import codecs
from tempfile import mkstemp
from shutil import move
from os import remove
def replace(source_file_path, pattern, substring):
fh, target_file_path = mkstemp()
with codecs.open(target_file_path, 'w', 'utf-8') as target_file:
with codecs.open(source_file_path, 'r', 'utf-8') as source_file:
for line in source_file:
target_file.write(line.replace(pattern, substring))
remove(source_file_path)
move(target_file_path, source_file_path)
Using hamishmcn's answer as a template I was able to search for a line in a file that match my regex and replacing it with empty string.
import re
fin = open("in.txt", 'r') # in file
fout = open("out.txt", 'w') # out file
for line in fin:
p = re.compile('[-][0-9]*[.][0-9]*[,]|[-][0-9]*[,]') # pattern
newline = p.sub('',line) # replace matching strings with empty string
print newline
fout.write(newline)
fin.close()
fout.close()
if you remove the indent at the like below, it will search and replace in multiple line.
See below for example.
def replace(file, pattern, subst):
#Create temp file
fh, abs_path = mkstemp()
print fh, abs_path
new_file = open(abs_path,'w')
old_file = open(file)
for line in old_file:
new_file.write(line.replace(pattern, subst))
#close temp file
new_file.close()
close(fh)
old_file.close()
#Remove original file
remove(file)
#Move new file
move(abs_path, file)
I have some problem to open and read a txt-file in Python. The txt file contains text (cat text.txt works fine in Terminal). But in Python I only get 5 empty lines.
print open('text.txt').read()
Do you know why?
I solved it. Was a utf-16 file.
print open('text.txt').read().decode('utf-16-le')
if this prints the lines in your file then perhaps the file your program is selecting is empty? I don't know, but try this:
import tkinter as tk
from tkinter import filedialog
import os
def fileopen():
GUI=tk.Tk()
filepath=filedialog.askopenfilename(parent=GUI,title='Select file to print lines.')
(GUI).destroy()
return (filepath)
filepath = fileopen()
filepath = os.path.normpath(filepath)
with open (filepath, 'r') as fh:
print (fh.read())
or alternatively, using this method of printing lines:
fh = open(filepath, 'r')
for line in fh:
line=line.rstrip('\n')
print (line)
fh.close()
or if you want the lines loaded into a list of strings:
lines = []
fh = open(filepath, 'r')
for line in fh:
line=line.rstrip('\n')
lines.append(line)
fh.close()
for line in lines:
print (line)
When you open file I think you have to specify how do you want to open it. In your example you should open it for reading like:
print open('text.txt',"r").read()
Hope this does the trick.
I should preface that I am a complete Python Newbie.
Im trying to create a script that will loop through a directory and its subdirectories looking for text files. When it encounters a text file it will parse the file and convert it to NITF XML and upload to an FTP directory.
At this point I am still working on reading the text file into variables so that they can be inserted into the XML document in the right places. An example to the text file is as follows.
Headline
Subhead
By A person
Paragraph text.
And here is the code I have so far:
with open("path/to/textFile.txt") as f:
#content = f.readlines()
head,sub,auth = [f.readline().strip() for i in range(3)]
data=f.read()
pth = os.getcwd()
print head,sub,auth,data,pth
My question is: how do I iterate through the body of the text file(data) and wrap each line in HTML P tags? For example;
<P>line of text in file </P> <P>Next line in text file</p>.
Something like
output_format = '<p>{}</p>\n'.format
with open('input') as fin, open('output', 'w') as fout:
fout.writelines( output_format(line.strip()) for line in fin )
This assumes that you want to write the new content back to the original file:
with open('path/to/textFile.txt') as f:
content = f.readlines()
with open('path/to/textFile.txt', 'w') as f:
for line in content:
f.write('<p>' + line.strip() + '</p>\n')
with open('infile') as fin, open('outfile',w) as fout:
for line in fin:
fout.write('<P>{0}</P>\n'.format(line[:-1]) #slice off the newline. Same as `line.rstrip('\n')`.
#Only do this once you're sure the script works :)
shutil.move('outfile','infile') #Need to replace the input file with the output file
in you case, you should probably replace
data=f.read()
with:
data = '\n'.join("<p>%s</p>" % l.strip() for l in f)
use data=f.readlines() here,
and then iterate over data and try something like this:
for line in data:
line="<p>"+line.strip()+"</p>"
#write line+'\n' to a file or do something else
append the and <\p> for each line
ex:
data_new=[]
data=f.readlines()
for lines in data:
data_new.append("<p>%s</p>\n" % data.strip().strip("\n"))
You could use the fileinput module to modify one or more files in-place, with optional backup file creation if desired (see its documentation for details). Here's it being used to process one file.
import fileinput
for line in fileinput.input('testinput.txt', inplace=1):
print '<P>'+line[:-1]+'<\P>'
The 'testinput.txt' argument could also be a sequence of two or more file names instead of just a single one, which could be useful especially if you're using os.walk() to generate the list of files in the directory and its subdirectories to process (as you probably should be doing).