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How to delete specific line in text file?

I'm making a joke program that has a text file storing jokes. On program load, it grabs all the lines from the file and assigns them to a jokes list Everything but the remove joke function is working. Whenever you call remove joke, it ends up re-writing every line in the text file to an empty string instead of the selected line
When running this function, it does remove the joke from the jokes list properly
def remove_joke():
for i in range(len(jokes)):
print(f"{i}\t{jokes[i]}")
remove_index = int(input("Enter the number of the joke you want to remove:\t"))
with open("jokes.txt", "r") as f:
lines = f.readlines()
with open("jokes.txt", "w") as f:
for line in lines:
print(line)
if line == jokes[remove_index]:
f.write("")
jokes.remove(jokes[remove_index])

Instead of
if line == jokes[remove_index]:
f.write("")
you want:
if line != jokes[remove_index]:
f.write(line+'\n')
Or even:
if line != jokes[remove_index]:
print(line, file=f)

Opening file vs reading file in python

I am attempting to print the file, split by line using two methods: one is using the method read on files and the second is using a for loop and splitting the files into lines. I am getting a Traceback error on the last line stating that "words" is not defined. I cannot see why this is the case.
fname = input('enter file name')
try:
fhandle = open(fname, 'r')
except:
print('file does not exist')
exit()
#store entire file in a variable called data
data = fhandle.read()
print(data)
#iterate through each line in a file handle
for line in fhandle:
line = line.strip()
words = line.split()
print(words)

When reading a file, Python keeps track of a cursor within the file. Data is read from the position of the cursor onwards, and reading moves the cursor forward to the end of the data that was read. This is so that, e.g., calling f.readline() twice will return the next line each time, rather than the first line both times.
When you call f.read(), the whole file is read, so the cursor is moved to the end of the file. Then, when you iterate through fhandle, Python only considers the lines ahead of the cursor — of which there are none. Since the object being iterated through is empty, the body of the for loop is never executed, so words is never assigned to.
You can fix this by calling fhandle.seek(0) directly before the for loop to return the cursor to the start of the file.
There is also a logical error in your program. If you want to print every line, not just the last, in your for loop, you need to indent print(words) so that it's in the for loop.
As a best practice, you should also call fhandle.close() when you're finished using the file.

words it not define because of read(), it makes for loop didn't return anything.
Python file method read() reads at most size bytes from the file. If
the read hits EOF before obtaining size bytes, then it reads only
available bytes.
When print(words) is indented in for loop, it just return nothing too. But if read() is removed while print(words) isn't indented, it'll return a list of the last line:
fname = input('enter file name')
try:
fhandle = open(fname, 'r')
except:
print('file does not exist')
exit()
# store entire file in a variable called data
# data = fhandle.read()
# print(data)
# iterate through each line in a file handle
for line in fhandle:
line = line.strip()
words = line.split()
print(words)
# ['Line', '4']
And if print(words) is indented while read() is removed, it'll return this:
fname = input('enter file name')
try:
fhandle = open(fname, 'r')
except:
print('file does not exist')
exit()
# store entire file in a variable called data
# data = fhandle.read()
# print(data)
# iterate through each line in a file handle
for line in fhandle:
line = line.strip()
words = line.split()
print(words)
# ['Line', '1']
# ['Line', '2']
# ['Line', '3']
# ['Line', '4']
I'm not sure what is your intent using split() but if you just want to print line by line using read(), your code already did that.
When using for loop, just comment or remove read() then just print line
fname = input('enter file name')
try:
fhandle = open(fname, 'r')
except:
print('file does not exist')
exit()
# store entire file in a variable called data
# data = fhandle.read()
# print(data)
# iterate through each line in a file handle
for line in fhandle:
print(line.strip())
# Line 1
# Line 2
# Line 3
# Line 4
But if you're intend to make a list consisted of each line, you can use splitlines()
fname = input('enter file name')
try:
fhandle = open(fname, 'r')
except:
print('file does not exist')
exit()
#store entire file in a variable called data
data = fhandle.read().splitlines()
print(data)
# ['Line 1', 'Line 2', 'Line 3', 'Line 4']
Hopes this help.

How to prompt user that asks a user for a file name?

I am going through Intro to Programming so basic stuff here, I have an assignment to "write a program that asks a user for a file name and then displays the first 5 lines of the file," I just can't figure out how to use the input command in this situation and then transfer to open()
Edit: Sorry here is a code snippet I had, I just don't get how to apply input from here.
def main():
#This function writes to the testFile.docx file
outfile = open('testFile.docx', 'w')
outfile.write('Hello World\n')
outfile.write('It is raining outside\n')
outfile.write('Ashley is sick\n')
outfile.write('My dogs name is Bailey\n')
outfile.write('My cats name is Remi\n')
outfile.write('Spam Eggs and Spam\n')
outfile.close()
infile = open('testFile.docx', 'r')
testFileContent = infile.read()
infile.close()
print(testFileContent)
main()

First, we ask for a filename. Then we use the try clause, which checks whether the file exists. If it does it will print 5 lines. If it does not, it will print No such a file found!
x = input('Enter a file name')
try:
with open(x) as f:
data = f.readlines()
for i in range(5):
print(data[i])
except:
print('No such a file found!')

Using a simple function,
def hello_user():
user_input = input('Enter file name: ')
try:
with open(user_input, 'r') as f:
data = f.readlines()
data = data[:5]
for o in data:
print(o.strip())
except FileNotFoundError:
print('Not found ')
hello_user()
It asks for a file name
If the file exists in the same directory the script is running, it opens the file and read each lines (white lines inclusive)
We select only the first 5 lines
We iterate through the list and remove the extra whitespace character(e.g \n).
If the file was not found, we catch the exception.

input() is used to receive input from the user. Once we recieve the input, we use the open() method to read the file in read mode.
def main():
file = input("Please enter a file name")
with open(file, 'r') as f:
lines = f.readlines()
print(lines[:5])
The with statement makes sure that it closes the file automatically without explicitly calling f.close()
The method f.readlines() returns an array containing the lines in the file.
The print() statement prints the first 5 lines of the file.

How to Open a file through python

I am very new to programming and the python language.
I know how to open a file in python, but the question is how can I open the file as a parameter of a function?
example:
function(parameter)
Here is how I have written out the code:
def function(file):
with open('file.txt', 'r') as f:
contents = f.readlines()
lines = []
for line in f:
lines.append(line)
print(contents)

You can easily pass the file object.
with open('file.txt', 'r') as f: #open the file
contents = function(f) #put the lines to a variable.
and in your function, return the list of lines
def function(file):
lines = []
for line in f:
lines.append(line)
return lines
Another trick, python file objects actually have a method to read the lines of the file. Like this:
with open('file.txt', 'r') as f: #open the file
contents = f.readlines() #put the lines to a variable (list).
With the second method, readlines is like your function. You don't have to call it again.
Update
Here is how you should write your code:
First method:
def function(file):
lines = []
for line in f:
lines.append(line)
return lines
with open('file.txt', 'r') as f: #open the file
contents = function(f) #put the lines to a variable (list).
print(contents)
Second one:
with open('file.txt', 'r') as f: #open the file
contents = f.readlines() #put the lines to a variable (list).
print(contents)
Hope this helps!

Python allows to put multiple open() statements in a single with. You comma-separate them. Your code would then be:
def filter(txt, oldfile, newfile):
'''\
Read a list of names from a file line by line into an output file.
If a line begins with a particular name, insert a string of text
after the name before appending the line to the output file.
'''
with open(newfile, 'w') as outfile, open(oldfile, 'r', encoding='utf-8') as infile:
for line in infile:
if line.startswith(txt):
line = line[0:len(txt)] + ' - Truly a great person!\n'
outfile.write(line)
# input the name you want to check against
text = input('Please enter the name of a great person: ')
letsgo = filter(text,'Spanish', 'Spanish2')
And no, you don't gain anything by putting an explicit return at the end of your function. You can use return to exit early, but you had it at the end, and the function will exit without it. (Of course with functions that return a value, you use the return to specify the value to return.)

def fun(file):
contents = None
with open(file, 'r') as fp:
contents = fp.readlines()
## if you want to eliminate all blank lines uncomment the next line
#contents = [line for line in ''.join(contents).splitlines() if line]
return contents
print fun('test_file.txt')
or you can even modify this, such a way it takes file object as a function arguement as well

Here's a much simpler way of opening a file without defining your own function in Python 3.4:
var=open("A_blank_text_document_you_created","type_of_file")
var.write("what you want to write")
print (var.read()) #this outputs the file contents
var.close() #closing the file
Here are the types of files:
"r": just to read a file
"w": just to write a file
"r+": a special type which allows both reading and writing of the file
For more information see this cheatsheet.

def main():
file=open("chirag.txt","r")
for n in file:
print (n.strip("t"))
file.close()
if __name__== "__main__":
main()
the other method is
with open("chirag.txt","r") as f:
for n in f:
print(n)

how access to a file concurrently to add/edit/delete the data?

I want to create a text file and add data to it, line by line. If a data line already exists in the file, it should be ignored. Otherwise, it should be appended to the file.

You are almost certainly better to read the file and write a new changed version. In most circumstances it will be quicker, easier, less error-prone and more extensible.

If your file isn't that big, you could just do something like this:
added = set()
def add_line(line):
if line not in added:
f = open('myfile.txt', 'a')
f.write(line + '\n')
added.add(line)
f.close()
But this isn't a great idea if you have to worry about concurrency, large amounts of data being stored in the file, or basically anything other than something quick and one-off.

I did it like this,
def retrieveFileData():
"""Retrieve Location/Upstream data from files"""
lines = set()
for line in open(LOCATION_FILE):
lines.add(line.strip())
return lines
def add_line(line):
"""Add new entry to file"""
f = open(LOCATION_FILE, 'a')
lines = retrieveFileData()
print lines
if line not in lines:
f.write(line + '\n')
lines.add(line)
f.close()
else:
print "entry already exists"
if __name__ == "__main__":
while True:
line = raw_input("Enter line manually: ")
add_line(line)
if line == 'quit':
break