File Methods

diagram what each file mode does the moment you open it mermaid

  flowchart TD
  A["open(path, mode)"] --> B{"mode"}
  B -->|"r"| C["read only; FileNotFoundError if missing"]
  B -->|"w"| D["TRUNCATES to 0 bytes immediately, creates if missing"]
  B -->|"a"| E["write only, always at the end; creates if missing"]
  B -->|"x"| F["create only; FileExistsError if it exists"]
  B -->|"r+"| G["read AND write, keeps the contents"]
  B -->|"w+"| H["read and write, but TRUNCATES first"]
  D --> I["the data is gone before you write a byte"]
  H --> I
  G --> J["this is the one people mean by 'open for editing'"]

Two of these destroy the file before your first write, which is why an accidental w where r was meant loses data even if the program then crashes. The distinction that matters is not read against write -- it is truncate against keep, and whether the file is required to exist.

w empties the file on open, before any write — measured

Opened against an existing 8-byte file, then checked the size immediately:

Mode	readable	writable	size right after open()
r	yes	no	8
w	no	yes	0
a	no	yes	8
x	—	—	FileExistsError
r+	yes	yes	8
w+	yes	yes	0

The file was empty before anything was written. So a program that opens in w, then raises while computing what to write, has already destroyed the original — and there is no undo.

If you want to read and then write the same file, r+ is the mode. If you want to be sure you are not overwriting something, x refuses rather than clobbering. And for anything valuable, write to a temporary file and os.replace it into position, so a crash leaves the original intact.

File Methods

This tutorial will cover the different methods that can be used to read and write to files.

Table of Methods

S.No.	Method	Description	Example
1	open()	Opens a file and returns a file object	file = open("file.txt", "r")
2	close()	Closes a file	file.close()
3	read()	Reads the entire file and returns a string	file.read()
4	readline()	Reads a single line from the file	file.readline()
5	readlines()	Reads all the lines from the file and returns a list	file.readlines()
6	write()	Writes a string to the file	file.write("Hello World")
7	writelines()	Writes a list of strings to the file	file.writelines(["Hello", "World"])
8	seek()	Changes the current position of the file pointer	file.seek(0)
9	tell()	Returns the current position of the file pointer	file.tell()
10	truncate()	Truncates the file to the given size	file.truncate(10)
11	flush()	Flushes the internal buffer	file.flush()
12	fileno()	Returns the file descriptor	file.fileno()
13	isatty()	Returns True if the file is connected to a terminal	file.isatty()

File Modes

The file modes are used to specify the purpose of opening a file. The following table lists the different file modes available in Python.

S.No.	Mode	Description
1	r	Opens a file for reading only. The file pointer is placed at the beginning of the file. This is the default mode.
2	rb	Opens a file for reading only in binary format. The file pointer is placed at the beginning of the file. This is the default mode.
3	r+	Opens a file for both reading and writing. The file pointer placed at the beginning of the file.
4	rb+	Opens a file for both reading and writing in binary format. The file pointer placed at the beginning of the file.
5	w	Opens a file for writing only. Overwrites the file if the file exists. If the file does not exist, creates a new file for writing.
6	wb	Opens a file for writing only in binary format. Overwrites the file if the file exists. If the file does not exist, creates a new file for writing.
7	w+	Opens a file for both writing and reading. Overwrites the existing file if the file exists. If the file does not exist, creates a new file for reading and writing.
8	wb+	Opens a file for both writing and reading in binary format. Overwrites the existing file if the file exists. If the file does not exist, creates a new file for reading and writing.
9	a	Opens a file for appending. The file pointer is at the end of the file if the file exists. If the file does not exist, it creates a new file for writing.
10	ab	Opens a file for appending in binary format. The file pointer is at the end of the file if the file exists. If the file does not exist, it creates a new file for writing.
11	a+	Opens a file for both appending and reading. The file pointer is at the end of the file if the file exists. If the file does not exist, it creates a new file for reading and writing.
12	ab+	Opens a file for both appending and reading in binary format. The file pointer is at the end of the file if the file exists. If the file does not exist, it creates a new file for reading and writing.
13	x	Creates a new file. If the file already exists, the operation fails.
14	x+	Creates a new file. If the file already exists, the operation fails.
15	xb	Creates a new file in binary format. If the file already exists, the operation fails.
16	xb+	Creates a new file in binary format. If the file already exists, the operation fails.
17	t	Opens in text mode. (default)
18	b	Opens in binary mode.
19	+	Opens a file for updating (reading and writing)
20	U	Universal newline mode.
21	rU	Opens a file for reading in universal newline mode. (deprecated)
22	wU	Opens a file for writing in universal newline mode. (deprecated)
23	rbU	Opens a file for reading in universal newline mode. (deprecated)
24	wbU	Opens a file for writing in universal newline mode. (deprecated)

File Object Attributes

The following table lists the different file object attributes available in Python.

S.No.	Attribute	Description
1	closed	Returns True if the file is closed, False otherwise.
2	encoding	Returns the encoding of the file.
3	mode	Returns the mode of the file.
4	name	Returns the name of the file.
5	newlines	Returns a tuple of all the line terminators in the file.
6	softspace	Returns False if space explicitly required with print, True otherwise.

open() Method

The open() method opens a file and returns a file object. The following example opens a file named “file.txt” in read mode and prints its content.

file.txt

Hello World

open.py

file = open("file.txt", "r")
 
print(file.read())

Output:

command

C:\Users\username>python open.py
Hello World

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The read() method reads the entire content of the file and returns it as a string.

close() Method

The close() method closes a file. A closed file cannot be read or written any more. Any operation, which requires that the file be opened will raise a ValueError after the file has been closed. Calling close() more than once is allowed.

file.txt

Hello World

close.py

file = open("file.txt", "r")
 
print(file.read())
file.close()

Output:

command

C:\Users\username>python close.py
Hello World

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The read() method reads the entire content of the file and returns it as a string. The close() method closes the file.

read() Method

The read() method reads the entire content of the file and returns it as a string. The following example opens a file named “file.txt” in read mode and prints its content.

file.txt

Hello World

read.py

file = open("file.txt", "r")
 
print(file.read())

Output:

command

C:\Users\username>python read.py
Hello World

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The read() method reads the entire content of the file and returns it as a string.

readline() Method

The readline() method reads a single line from the file. The following example opens a file named “file.txt” in read mode and prints its first line.

file.txt

Hello World

readline.py

file = open("file.txt", "r")
 
print(file.readline())

Output:

command

C:\Users\username>python readline.py
Hello World

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The readline() method reads the first line of the file and returns it as a string.

readlines() Method

The readlines() method reads all the lines from the file and returns a list. The following example opens a file named “file.txt” in read mode and prints all its lines.

file.txt

Hello World
Hii World

readlines.py

file = open("file.txt", "r")
 
print(file.readlines())

Output:

command

C:\Users\username>python readlines.py
['Hello World\n', 'Hii World']

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The readlines() method reads all the lines from the file and returns a list.

write() Method

The write() method writes a string to the file. The following example opens a file named “file.txt” in write mode and writes a string to it.

write.py

file = open("file.txt", "w")
 
file.write("Hello World")

Output:

command

C:\Users\username>python write.py

file.txt

Hello World

In the above example, we open a file named “file.txt” in write mode. The file object is stored in the variable file. The write() method writes a string to the file.

writelines() Method

The writelines() method writes a list of strings to the file. The following example opens a file named “file.txt” in write mode and writes a list of strings to it.

writelines.py

file = open("file.txt", "w")
 
file.writelines(["Hello", "World"])

Output:

command

C:\Users\username>python writelines.py

file.txt

HelloWorld

In the above example, we open a file named “file.txt” in write mode. The file object is stored in the variable file. The writelines() method writes a list of strings to the file.

seek() Method

The seek() method changes the current position of the file pointer. The following example opens a file named “file.txt” in read mode and changes the current position of the file pointer.

file.txt

Hello World

seek.py

file = open("file.txt", "r")
 
file.seek(6)
print(file.read())

Output:

command

C:\Users\username>python seek.py
World

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The seek() method changes the current position of the file pointer to 6. The read() method reads the content of the file from the current position of the file pointer.

tell() Method

The tell() method returns the current position of the file pointer. The following example opens a file named “file.txt” in read mode and prints the current position of the file pointer.

file.txt

Hello World

tell.py

file = open("file.txt", "r")
 
file.seek(6)
print(file.tell())

Output:

command

C:\Users\username>python tell.py
6

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The seek() method changes the current position of the file pointer to 6. The tell() method returns the current position of the file pointer.

truncate() Method

The truncate() method truncates the file to the given size. The following example opens a file named “file.txt” in read mode and truncates it to 10 bytes.

file.txt

Hello World

truncate.py

file = open("file.txt", "r+")
 
file.truncate(10)
print(file.read())

Output:

command

C:\Users\username>python truncate.py
Hello Wor

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The truncate() method truncates the file to 10 bytes. The read() method reads the content of the file.

flush() Method

The flush() method flushes the internal buffer. The following example opens a file named “file.txt” in write mode and flushes the internal buffer.

flush.py

file = open("file.txt", "w")
 
file.write("Hello World")
file.flush()

Output:

command

C:\Users\username>python flush.py

file.txt

Hello World

In the above example, we open a file named “file.txt” in write mode. The file object is stored in the variable file. The write() method writes a string to the file. The flush() method flushes the internal buffer.

fileno() Method

The fileno() method returns the file descriptor. The following example opens a file named “file.txt” in read mode and prints its file descriptor.

file.txt

Hello World

fileno.py

file = open("file.txt", "r")
 
print(file.fileno())

Output:

command

C:\Users\username>python fileno.py
3

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The fileno() method returns the file descriptor.

isatty() Method

The isatty() method returns True if the file is connected to a terminal, False otherwise. The following example opens a file named “file.txt” in read mode and prints True if the file is connected to a terminal, False otherwise.

file.txt

Hello World

isatty.py

file = open("file.txt", "r")
 
print(file.isatty())

Output:

command

C:\Users\username>python isatty.py
False

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The isatty() method returns False because the file is not connected to a terminal.

closed Attribute

The closed attribute returns True if the file is closed, False otherwise. The following example opens a file named “file.txt” in read mode and prints True if the file is closed, False otherwise.

file.txt

Hello World

closed.py

file = open("file.txt", "r")
 
print(file.closed)
file.close()
print(file.closed)

Output:

command

C:\Users\username>python closed.py
False
True

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The closed attribute returns False because the file is not closed. The close() method closes the file. The closed attribute returns True because the file is closed.

encoding Attribute

The encoding attribute returns the encoding of the file. The following example opens a file named “file.txt” in read mode and prints its encoding.

file.txt

Hello World

encoding.py

file = open("file.txt", "r")
 
print(file.encoding)

Output:

command

C:\Users\username>python encoding.py
cp1252

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The encoding attribute returns the encoding of the file.

mode Attribute

The mode attribute returns the mode of the file. The following example opens a file named “file.txt” in read mode and prints its mode.

file.txt

Hello World

mode.py

file = open("file.txt", "r")
 
print(file.mode)

Output:

command

C:\Users\username>python mode.py
r

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The mode attribute returns the mode of the file.

name Attribute

The name attribute returns the name of the file. The following example opens a file named “file.txt” in read mode and prints its name.

file.txt

Hello World

name.py

file = open("file.txt", "r")
 
print(file.name)

Output:

command

C:\Users\username>python name.py
file.txt

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The name attribute returns the name of the file.

newlines Attribute

The newlines attribute returns a tuple of all the line terminators in the file. The following example opens a file named “file.txt” in read mode and prints its line terminators.

file.txt

Hello World
Hii World

newlines.py

file = open("file.txt", "r")
 
print(file.newlines)

Output:

command

C:\Users\username>python newlines.py
('\r\n', '\r\n')

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The newlines attribute returns a tuple of all the line terminators in the file.

softspace Attribute

The softspace attribute returns False if space explicitly required with print, True otherwise. The following example opens a file named “file.txt” in read mode and prints False if space explicitly required with print, True otherwise.

file.txt

Hello World

softspace.py

file = open("file.txt", "r")
 
print(file.softspace)
print("Hello World")
print(file.softspace)

Output:

command

C:\Users\username>python softspace.py
False
Hello World
True

In the above example, we open a file named “file.txt” in read mode. The file object is stored in the variable file. The softspace attribute returns False because space explicitly required with print. The print() function prints “Hello World”. The softspace attribute returns True because space is not explicitly required with print.

Conclusion

In this tutorial, you learned about the different methods that can be used to read and write to files. In the next tutorial, you will learn about the different file attributes that can be used to get information about a file. For more information on the file methods, refer to the official documentation. For more tutorials, visit our Python Central Hub.

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sketch What open() does to the file before you write anything p5.js Pause Restart

An existing file of eight bytes, opened in each mode. The bar is the file on disk and it updates at the moment open() returns, not when you write. Two of the six modes empty it immediately, which is why a program that opens in w and then crashes has already destroyed the data. Sizes measured on a real file.

Check yourself

pch.quizTag pch.quizDefaultTitle

1. You open an existing 8-byte file with mode `'w'` and then, before writing, your program raises. What is in the file?

   A The original 8 bytes B Nothing — it was truncated when it was opened C 8 bytes of null characters D It depends on the operating system
   pch.quizShowAnswer

   B — Nothing — it was truncated when it was opened — `w` truncates on open, before any write. Measured: the file was 0 bytes immediately after `open()`. There is no undo.

2. Which mode lets you read AND write without destroying the existing contents?

   A `w+` B `r+` C `a+` D `w`
   pch.quizShowAnswer

   B — `r+` — `r+` opens for reading and writing and keeps the contents. `w+` is also read/write but truncates first — measured at 0 bytes on open.

3. What does mode `'x'` do when the file already exists?

   A Truncates it B Appends to it C Raises FileExistsError D Creates a numbered copy
   pch.quizShowAnswer

   C — Raises FileExistsError — `x` is create-only. It refuses rather than clobbering, which makes it the safe choice when overwriting would be a bug.

4. What is the safest way to replace a file's contents when the data matters?

   A Open it with `w` and write carefully B Write to a temporary file, then `os.replace` it into position C Open with `r+` and truncate at the end D Take a backup with `shutil.copy` first
   pch.quizShowAnswer

   B — Write to a temporary file, then `os.replace` it into position — Writing elsewhere and replacing means a crash mid-write leaves the original intact. `os.replace` is atomic on the same filesystem, and is consistent across platforms unlike `os.rename`.

Try it: File Methods Exercises

Exercise 1 – readline() vs readlines()

pch.exerciseTag pch.exerciseTitle

Exercise 2 – tell() and seek()

pch.exerciseTag pch.exerciseTitle

Exercise 3 – writelines()

pch.exerciseTag pch.exerciseTitle