Which of the following command is used to open a file in write mode only?

When we want to read from or write to a file, we need to open it first. When we are done, it needs to be closed so that the resources that are tied with the file are freed.

Hence, in Python, a file operation takes place in the following order:

1. Open a file
2. Read or write [perform operation]
3. Close the file

Opening Files in Python

In Python, we use the

file1 = open["test.txt", "r"]

1 method to open files.

To demonstrate how we open files in Python, let's suppose we have a file named

file1 = open["test.txt", "r"]

2 with the following content.

Opening Files in Python

Now, let's try to open data from this file using the

file1 = open["test.txt", "r"]

1 function.

# open file in current directory
file1 = open["test.txt"]

Here, we have created a file object named file1. This object can be used to work with files and directories.

By default, the files are open in read mode [cannot be modified]. The code above is equivalent to

file1 = open["test.txt", "r"]

Here, we have explicitly specified the mode by passing the

file1 = open["test.txt", "r"]

4 argument which means file is opened for reading.

Different Modes to Open a File in Python

ModeDescription

file1 = open["test.txt", "r"]

5Open a file for reading. [default]

file1 = open["test.txt", "r"]

6Open a file for writing. Creates a new file if it does not exist or truncates the file if it exists.

file1 = open["test.txt", "r"]

7Open a file for exclusive creation. If the file already exists, the operation fails.

file1 = open["test.txt", "r"]

8Open a file for appending at the end of the file without truncating it. Creates a new file if it does not exist.

file1 = open["test.txt", "r"]

9Open in text mode. [default]

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

0Open in binary mode.

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

1Open a file for updating [reading and writing]

Here's few simple examples of how to open a file in different modes,

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

Reading Files in Python

After we open a file, we use the

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

2 method to read its contents. For example,

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

Output

This is a test file.
Hello from the test file.

In the above example, we have read the

file1 = open["test.txt", "r"]

2 file that is available in our current directory. Notice the code,

read_content = file1.read

Here,

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

4 reads the

file1 = open["test.txt", "r"]

2 file and is stored in the read_content variable.

Closing Files in Python

When we are done with performing operations on the file, we need to properly close the file.

Closing a file will free up the resources that were tied with the file. It is done using the

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

6 method in Python. For example,

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

# close the file
file1.close[]

Output

This is a test file.
Hello from the test file.

Here, we have used the

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

6 method to close the file.

After we perform file operation, we should always close the file; it's a good programming practice.

Exception Handling in Files

If an exception occurs when we are performing some operation with the file, the code exits without closing the file. A safer way is to use a try...finally block.

Let's see an example,

try:
    file1 = open["test.txt", "r"]
    read_content = file1.read[]
    print[read_content]

finally:
    # close the file
    file1.close[]

Here, we have closed the file in the

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

8 block as

file1 = open["test.txt"]      # equivalent to 'r' or 'rt'
file1 = open["test.txt",'w']  # write in text mode
file1 = open["img.bmp",'r+b'] # read and write in binary mode

8 always executes, and the file will be closed even if an exception occurs.

Use of with...open Syntax

In Python, we can use the

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

0 syntax to automatically close the file. For example,

with open["test.txt", "r"] as file1:
    read_content = file1.read[]
    print[read_content]

Note: Since we don't have to worry about closing the file, make a habit of using the

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

0 syntax.

Writing to Files in Python

There are two things we need to remember while writing to a file.

• If we try to open a file that doesn't exist, a new file is created.
• If a file already exists, its content is erased, and new content is added to the file.

In order to write into a file in Python, we need to open it in write mode by passing

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

2 inside

file1 = open["test.txt", "r"]

1 as a second argument.

Suppose, we don't have a file named test2.txt. Let's see what happens if we write contents to the

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

4 file.

file1 = open["test.txt", "r"]

0

Here, a new

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

4 file is created and this file will have contents specified inside the

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

6 method.

Writing to Python Files

Python File Methods

There are various methods available with the file object. Some of them have been used in the above examples.

Here is the complete list of methods in text mode with a brief description:

MethodDescriptionclose[]Closes an opened file. It has no effect if the file is already closed.detach[]Separates the underlying binary buffer from the

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

7 and returns it.fileno[]Returns an integer number [file descriptor] of the file.flush[]Flushes the write buffer of the file stream.isatty[]Returns

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

8 if the file stream is interactive.read[n]Reads at most n characters from the file. Reads till end of file if it is negative or

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

9.readable[]Returns

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

8 if the file stream can be read from.readline[n=-1]Reads and returns one line from the file. Reads in at most n bytes if specified.readlines[n=-1]Reads and returns a list of lines from the file. Reads in at most n bytes/characters if specified.seek[offset,from=

This is a test file.
Hello from the test file.

1]Changes the file position to offset bytes, in reference to from [start, current, end].seekable[]Returns

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

8 if the file stream supports random access.tell[]Returns an integer that represents the current position of the file's object.truncate[size=

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

9]Resizes the file stream to size bytes. If size is not specified, resizes to current location.writable[]Returns

# open a file
file1 = open["test.txt", "r"]

# read the file
read_content = file1.read[]
print[read_content]

8 if the file stream can be written to.write[s]Writes the string s to the file and returns the number of characters written.writelines[lines]Writes a list of lines to the file.

Which command is used to open a file?

Which of the command is used to open a file c :\ temp txt in write mode only?

Which of the following command is used to open a file c demo txt in read mode only in Python?