I have a file that I open and i want to search through till I find a specific text phrase at the beginning of a line. I then want to overwrite that line with 'sentence'
sentence = "new text" "
with open(main_path,'rw') as file: # Use file to refer to the file object
for line in file.readlines():
if line.startswith('text to replace'):
file.write(sentence)
I'm getting:
Traceback (most recent call last):
File "setup_main.py", line 37, in <module>
with open(main_path,'rw') as file: # Use file to refer to the file object
ValueError: must have exactly one of create/read/write/append mode
How can I get this working?
You can open a file for simultaneous reading and writing but it won't work the way you expect:
with open('file.txt', 'w') as f:
f.write('abcd')
with open('file.txt', 'r+') as f: # The mode is r+ instead of r
print(f.read()) # prints "abcd"
f.seek(0) # Go back to the beginning of the file
f.write('xyz')
f.seek(0)
print(f.read()) # prints "xyzd", not "xyzabcd"!
You can overwrite bytes or extend a file but you cannot insert or delete bytes without rewriting everything past your current position.
Since lines aren't all the same length, it's easiest to do it in two seperate steps:
lines = []
# Parse the file into lines
with open('file.txt', 'r') as f:
for line in f:
if line.startswith('text to replace'):
line = 'new text\n'
lines.append(line)
# Write them back to the file
with open('file.txt', 'w') as f:
f.writelines(lines)
# Or: f.write(''.join(lines))
You can't read and write to the same file. You'd have to read from main_path, and write to another one, e.g.
sentence = "new text"
with open(main_path,'rt') as file: # Use file to refer to the file object
with open('out.txt','wt') as outfile:
for line in file.readlines():
if line.startswith('text to replace'):
outfile.write(sentence)
else:
outfile.write(line)
Not the problem with the example code, but wanted to share as this is where I wound up when searching for the error.
I was getting this error due to the chosen file name (con.txt for example) when appending to a file on Windows. Changing the extension to other possibilities resulted in the same error, but changing the file name solved the problem. Turns out the file name choice caused a redirect to the console, which resulted in the error (must have exactly one of read or write mode): Why does naming a file 'con.txt' in windows make Python write to console, not file?
Related
I tried running this code in python. I ensured:
The .txt file was in the same file as the code file and the file name was "random.txt" saved in .txt format
file = input ('Enter File:')
if len(file) < 1 : file = 'random.txt'
fhan = open(file)
print (fhan)
My command prompt returned me <_io.TextIOWrapper name='random.txt' mode='r' encoding='cp1252'> with no traceback. I don't know how to get the file to open and print the content
Open a file, and print the file content:
with open('./demo.txt', 'r') as file:
txt = file.read()
print(txt)
fhan is a file handle, so printing it simply prints the results of calling its repr method, which shows what you see. To read the entire file, you can call fhan.read().
It's also good practice to use a with statement to manage resources. For example, your code can be written as
file = input('Enter File:')
if not file: # check for empty string
file = 'random.txt'
with open(file, 'r') as fhan: # use the `with` statement
print(fhan.read())
The benefit of this syntax is that you'll never have to worry about forgetting to close the file handle.
I have an 11GB CSV file which has some corrupt lines I have to delete, I have identified the corrupted lines numbers from an ETL interface.
My program runs with small datasets, however, when I want to run on the main file I'm getting MemoryError. Below the code I'm using Do you have any suggestion to make it work?
row_to_delete = 101068
filename = "EKBE_0_20180907_065907 - Copy.csv"
with open(filename, 'r', encoding='utf8' ,errors='ignore') as file:
data = file.readlines()
print(data[row_to_delete -1 ])
data [row_to_delete -1] = ''
with open(filename, 'wb',encoding="utf8",errors='ignore') as file:
file.writelines( data )
Error:
Traceback (most recent call last):
File "/.PyCharmCE2018.2/config/scratches/scratch_7.py", line 7, in <module>
data = file.readlines()
MemoryError
Rather than read the whole list into memory, loop over the input file, and write all lines except the line you need to delete to the a new file. Use enumerate() to keep a counter if you need to delete by index:
row_to_delete = 101068
filename = "EKBE_0_20180907_065907 - Copy.csv"
with open(filename, 'r', encoding='utf8', errors='ignore') as inputfile,\
open(filename + '.fixed', 'wb', encoding="utf8") as outputfile:
for index, line in enumerate(inputfile):
if index == row_to_delete:
continue # don't write the line that matches
outputfile.writeline(line)
Rather than use an index, you could even detect a bad line directly in code this way.
Note that this writes to a new file, with the same name but with .fixed added.
You can move that file back to replace the old file if you want to, with os.rename(), once you are done copying all but the bad line:
os.rename(filename + '.fixed', filename)
Could someone give me some guidance on how you would get the contents of your text file on my python code without opening up the text file in another window?
Just point me in the right direction on how I should do it (No need for solutions)
with open(workfile, 'r') as f:
for line in f:
print line
If you don't use the context manager (the with statement) you will need to explicitly call f.close(), for example:
f = open('workfile', 'r')
line = f.readline()
print line
f.close()
file = open("your_file.txt", "r")
file.read()
The context is the following one, I have two text file that I need to edit.
I open the first text file read it line by line and edit it but sometimes when I encounter a specific line in the first text file I need to overwritte content of the the second file.
However, each time I re-open the second text file instead of overwritting its content the below code appends it to the file...
Thanks in advance.
def edit_custom_class(custom_class_path, my_message):
with open(custom_class_path, "r+") as file:
file.seek(0)
for line in file:
if(some_condition):
file.write(mu_message)
def process_file(file_path):
with open(file_path, "r+") as file:
for line in file:
if(some_condition):
edit_custom_class(custom_class_path, my_message)
In my opinion, simultaneously reading and modifying a file is a bad thing to do. Consider using something like this. First read the file, make modifications, and then overwrite the file completely.
def modify(path):
out = []
f = open(path)
for line in f:
if some_condition:
out.append(edited_line) #make sure it has a \n at the end
else:
out.append(original_line)
f.close()
with open(path,'w') as f:
for line in out:
f.write(line)
I was wondering how to make a .text file so I can put words in it and then in my program open the file. I just need to know how to make a .text file!
Anyone know why my code won't open my .txt file when I try to run it?
def readWords(filename):
words = []
wordFile = open(words.txt, "r")
for line in wordFile:
line = line.upper()
words.extend(string.split(line))
wordFile.close()
return words
with open('myfile.txt', 'w') as f:
f.write('potato')
Opening a file in write mode will create it for you if it doesn't already exist:
with open("/path/to/file.txt", "w") as myfile:
# Do whatever
In the above code, myfile will be the file object.
Here is a reference on open and one on with.