I need to write function which given a text file object open in read and write mode and a string, inserts the text of the string in the file at the current read/write position. In other words, the function writes the string in the file without overwriting the rest of it. When exiting the function, the new read/write position has to be exactly at the end of the newly inserted string.
The algorithm is simple; the function needs to:
read the content of the file starting at the current read/write position
write the given string at the same position step 1 started
write the content read at step 1. at the position where step 2. ended
reposition the read/write cursor at the same position step2. ended (and step 3. started)
If the argument file object is not readable or writable, the function should print a message and return immediately without changing anything.
This can be achieved by using the methods file object methods readable() and writable().
In the main script:
1- prompt the user for a filename
2- open the file in read-write mode. If the file is not found, print a message and exit the program
3- insert the filename as the first line of the file followed by an empty line
4- insert a line number and a space, at the beginning of each line of the original text.
I'm very confused on how to write the function and main body.
so far I only have
def openFile(fileToread):
print(file.read())
givefile = input("enter a file name: ")
try:
file = open(givefile, "r+")
readWriteFile = openFile(file)
except FileNotFoundError:
print("File does not exist")
exit(1)
print(givefile, "\n")
which is not a lot.
I need an output like this:
twinkle.txt
1 Twinkle, twinkle, little bat!
2 How I wonder what you're at!
3 Up above the world you fly,
4 Like a teatray in the sky.
the file used is a simple .txt file with the twinkle twinkle song
How can I do this?
Basic solution
give_file = input("enter a file name: ")
def open_file(file):
return file.read()
def save_file(file, content):
file.write(content)
try:
# Use this to get the data of the file
with open(give_file, "r") as fd:
file_content = open_file(fd)
except FileNotFoundError:
print("File does not exist")
exit(1)
# change the data
new_content = f'{give_file}\n\n{file_content}'
try:
# save the data
with open(give_file, "w") as fd:
save_file(fd, new_content)
except FileNotFoundError:
print("File does not exist")
exit(1)
This should give you the expected result.
I asked about the r+ and how to use it in this case. I got this answer:
reset the cursor to 0 should do the trick
my_fabulous_useless_string = 'POUET'
with open(path, 'r+') as fd:
content = fd.read()
fd.seek(0)
fd.write(f'{my_fabulous_useless_string}\n{content}')
so with your code it's:
give_file = input("enter a file name: ")
def open_file(file):
return file.read()
def save_file(file, content):
file.write(content)
try:
# Use this to get the data of the file
with open(give_file, "+r") as fd:
file_content = open_file(fd)
new_content = f'{give_file}\n\n{file_content}'
fd.seek(0)
save_file(fd, new_content)
except FileNotFoundError:
print("File does not exist")
exit(1)
A suggestion
Don't use function, it hide the fact that a method is used with some side-effects (move the cursor).
Instead, call the method directly, this is better:
give_file = input("enter a file name: ")
try:
# Use this to get the data of the file
with open(give_file, "+r") as fd:
file_content = fd.read()
new_content = f'{give_file}\n\n{file_content}'
fd.seek(0)
fd.write(new_content)
except FileNotFoundError:
print("File does not exist")
exit(1)
Or, with the basic solution and functions
def open_file(path):
with open(path, "r") as fd:
return fd.read()
def save_file(path, content):
with open(path, 'w') as fd:
fd.write(content)
# get file_name
file_name = input("enter a file name: ")
try:
# Use this to get the data of the file
file_content = open_file(file_name)
except FileNotFoundError:
print("File does not exist")
exit(1)
# change the data
new_content = f'{file_name}\n\n{file_content}'
# save the data
save_file(file_name, new_content)
Related
As the title says, I made a file editing program with python.
Here is the code that I'm have a problem with:
#fileEditing.py
def fileError(file):
raise OSError("file {} does not exist".format(file))
class AccessFile():
def fileExists(self, file):
import os
return bool(os.path.exists(file))
def filecreate(self, file):
if not self.fileExists(file):
with open(file, "w") as f:
f.close()
else: raise OSError("file {} already exists".format(file))
def filedelete(self, file):
import os
if self.fileExists(file):
os.remove(file)
else: fileError(file)
def fileread(self, file):
#check if file exists
if self.fileExists(file):
#detect length of file
with open(file, "r") as f:
line = " "
x = 0
while line != "":
line = f.readline()
x += 1
#piece lines together in a list
filelines = []
with open(file, "r") as f:
for i in range(x - 1):
filelines.append(str(f.readline()))
#return a tuple
return tuple(filelines)
else: fileError(file)
def filewrite(self, file, line, text):
''' BUG: apparently this either overwrites the line its writing or appends
to the line its writing... make up your mind!'''
if self.fileExists(file):
#get file contents
filelines = list(self.fileread(file))
#see if line parameter is out of range or not
try:
filelines[line] = text
except IndexError:
for i in range(line - len(filelines)):
filelines.append("")
filelines.append(str(text) + "\n")
#apply changes
with open(file, "w") as f:
f.write("") #delete contents
with open(file, "w") as f:
for l in filelines:
f.write(l)
else: fileError(file)
def fileoverwrite(self, file, data):
#if there is no file to delete, it will make a new one
try:
self.filedelete(file)
except:
pass
self.filecreate(file)
x = 0
for line in data:
print(line)
self.filewrite(file, x, line)
x += 1
accessfile = AccessFile()
The bug is in the filewrite(self, file, line, text) function. When called, it either writes a new line (which is what I want it to do), appends to the line its supposed to replace, or just doesn't write any lines at all.
Say I want to write a python file with this program:
#pytesting.py
from fileEditing import *
file = "/Users/ashton/Desktop/Atom/Python/FileEditing/FileManager.py"
data = [
"from fileEditing import *",
"",
"class FileEditing():",
" def __init__(options, immutable_files):",
" self.options, self.immutable_files = options, immutable_files",
" ",
" def prompt():",
" ",
"",
"while True:",
" pass"
]
accessfile.fileoverwrite(file, data)
When I run it, it makes a file with accessfile.fileoverwrite(file, data), like its supposed to.
But thats where things get whacky.
(FileManager.py below)
from fileEditing import *
class FileEditing():
def __init__(options, immutable_files): self.options, self.immutable_files = options, immutable_files
def prompt():
while True:
If you know how to fix the filewrite(self, file, line, text), please let me know.
(I use python 2.7 but python 3 is fine)
So this is definitely a Python 3.x solution but you said that it is fine, don't know if it will work in Python 2.x but it is so simple it should:
def file_overwrite(self, file, data):
with open(file, 'w') as file:
file.write('\n'.join(data))
And you seemingly also need to fix that data list because it is missing a few commas. Also the fact that this is all in a class is a bit weird, you do nothing with the instance, they all might as well be separate functions or #classmethods or #staticmethods. Also several things could be improved with your other functions. For example you shouldn't open the file twice and count its lines to read it. Just do file.readlines() at it will return a list of all lines:
def fileread(self, file):
if self.fileExists(file):
with open(file) as file:
return file.readlines()
else:
fileError(file)
Then also import os once at the start of the file, you don't need to import it in every function where you use os, also:
with open(file, "w") as f:
f.close()
f.close() is completely pointless because the context manger closes the file anyways and also there is mode "x" which is specifically made for file creation and will raise an error if the file already exists: https://www.w3schools.com/python/python_file_handling.asp
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.
This question already has answers here:
How do I append to a file?
(13 answers)
Closed 6 years ago.
I want to read and write files multiple times.But the way is failed,it only writes the last modified content rather than all modified contents.
The incorrect program
def openfile():
txt = open("test.txt", "r")
contents = txt.readlines()
txt.close()
return contents
def write_file(contents,f):
old_contents = openfile()
old_contents.insert(1,contents)
contents = "".join(old_contents )
f.write(contents)
f.close()
text1 = open("test.txt","w")
contents= "test1 \n"
write_file(contents,text1)
text2 = open("test.txt","w")
contents = "test2 \n"
write_file(contents,text2)**
Worry Output
test2
My hope output
test1
test2
This is too much of code for the File Open and Write, You can just use this following lines to append the text in your file
def FileSave(filename,content):
with open(filename, "a") as myfile:
myfile.write(content)
FileSave("test.txt","test1 \n")
FileSave("test.txt","test2 \n")
Here, when we using this line open(filename, "a"), the a indicates the appending the file, that means allow to insert extra data to the existing file
as stated in the python doc you need to open your file with mode='a' if you want to append to existing data; mode='w' simply overwrites:
with open(file='_test.txt', mode='a') as file:
file.write('test')
(if you are using python 2, change the variable name file above to something else; in python 2 file is a keyword).
The reason for your "Worry Output" is that you re-open "test.txt" in read mode inside openfile after you've already opened it in write mode outside the functions. When you open a file in write mode it gets truncated, i.e., the file pointer is positioned to the start of the file and the current contents of the file are discarded. So when you call openfile inside write_file the file is empty, and thus openfile returns an empty list.
Here's a repaired version of your code. We use try... except in openfile so we can return an empty list if the file doesn't exist.
def openfile(fname):
try:
f = open(fname, "r")
contents = f.readlines()
f.close()
return contents
except FileNotFoundError:
return []
def write_file(contents, fname):
old_contents = openfile(fname)
old_contents.insert(1,contents)
contents = "".join(old_contents)
f = open(fname, "w")
f.write(contents)
f.close()
contents= "test1 \n"
write_file(contents, "test.txt")
contents = "test2 \n"
write_file(contents, "test.txt")
And here are the contents of "test.txt" after running that code:
test1
test2
Actually, it's better to use with when opening files:
def openfile(fname):
try:
with open(fname, "r") as f:
contents = f.readlines()
return contents
except FileNotFoundError:
return []
def write_file(contents, fname):
old_contents = openfile(fname)
old_contents.insert(1,contents)
contents = "".join(old_contents)
with open(fname, "w") as f:
f.write(contents)
However, a much better way to do this is to simply open the file in append mode as hiro protagonist and K.Suthagar have already shown. But I figured it was a good idea to explain why your current code didn't do what you expected it to do.
text1 = open("test.txt","w")
It is because above code resets the content. "w" is to override the file content.
Below code should explain you where you went wrong-
def openfile():
txt = open("test.txt", "r")
contents = txt.readlines()
print "Openfile method- Contents: "+str(contents)
txt.close()
return contents
def write_file(contents,f):
print "WriteFile method- Content received: "+str(contents)
old_contents = openfile()
print "Writefile method- Old content read from file: "+str(old_contents)
old_contents.insert(1,contents)
print "Writefile method- Old content after insertion: "+str(old_contents)
contents = "".join(old_contents )
print "WriteFile method- Content to write: "+str(contents)
f.write(contents)
f.close()
text1 = open("test.txt","w")
contents= "test1 \n"
write_file(contents,text1)
text2 = open("test.txt","w")
contents = "test2 \n"
write_file(contents,text2)
As mentioned, use "a" to append to file.
Im having trouble printing the return value of one of my functions
def readfile(filename):
'''
Reads the entire contents of a file into a single string using
the read() method.
Parameter: the name of the file to read (as a string)
Returns: the text in the file as a large, possibly multi-line, string
'''
try:
infile = open(filename, "r") # open file for reading
# Use Python's file read function to read the file contents
filetext = infile.read()
infile.close() # close the file
return filetext # the text of the file, as a single string
except IOError:
()
def main():
''' Read and print a file's contents. '''
file = input(str('Name of file? '))
readfile(file)
How do I save readfile's value into a different variable then print the value of the variable where you saved readfile's return value?
This is the simplest way, I wont recommend adding a try block in the function because you will have to use it anyways after or return a empty value which is a bad thing
def readFile(FileName):
return open(FileName).read()
def main():
try:
File_String = readFile(raw_input("File name: "))
print File_String
except IOError:
print("File not found.")
if __name__ == "__main__":
main()
Have you tried:
def main():
''' Read and print a file's contents. '''
file = input(str('Name of file? '))
read_contents = readfile(file)
print read_contents
def main():
''' Read and print a file's contents. '''
file = input(str('Name of file? '))
text = readfile(file)
print text
this should do it, just assign the functions call to a variable.
But in case when the exception is raised you're returning nothing, so the function will return None.
def main():
''' Read and print a file's contents. '''
file = input('Name of file? ') #no need of str() here
foo=readfile(file)
print foo
and use with statement when handling files, it takes care of the closing of the file:
def readfile(filename):
try:
with open(filename) as infile :
filetext = infile.read()
return filetext
except IOError:
pass
#return something here too
properties = ["color", "font-size", "font-family", "width", "height"]
inPath = "style.css"
outPath = "output.txt"
#Open a file for reading
file = open(inPath, 'rU')
if file:
# read from the file
filecontents = file.read()
file.close()
else:
print "Error Opening File."
#Open a file for writing
file = open(outPath, 'wb')
if file:
for i in properties:
search = i
index = filecontents.find(search)
file.write(str(index), "\n")
file.close()
else:
print "Error Opening File."
seems to work, but:
It only searches a keyword once?
Its not writing to the output file. function takes exactly 1 argument
I don't want it to print the index actually, but the number of time the keyword appears.
Many thanks
First, you want .count(search), not .find(search), if what you're looking for is # of occurrences.
Second, .write() only takes a single parameter - if you want to write a newline, you need to concatenate it first, or call .write() twice.
Third, doing for i in properties: search = i is redundant; just use the name you want in your for loop.
for search in properties:
cnt = filecontents.count(search)
file.write(str(cnt) + "\n")
from itertools import imap
properties = ("color", "font-size", "font-family", "width", "height")
inPath = "style.css"
outPath = "output.txt"
try:
#Open a file for reading
filecontents = file(inPath).read()
except Exception as exc:
print exc
else:
#Open a file for writing
with open(outPath, 'wb') as out_file:
#for property in properties:
# out_string = "%s %s\n"
# out_file.write( out_string % (
# property, filecontents.count(property)))
outfile.write('\n'.join(
imap(str, imap(filecontents.count, properties))))