Reading and Writing Files

For a more in-depth look at file and directory path manipulation, see the File and directory Paths page.

The file Reading/Writing process

To read/write to a file in Python, you will want to use the with statement, which will close the file for you after you are done, managing the available resources for you.

Opening and reading files

The open function opens a file and return a corresponding file object.

# Read file using 'with' statement: automatically closes file when done
with open('/home/labex/project/hi.txt') as hello_file:
    hello_content = hello_file.read()  # Read entire file content

hello_content

'Hello World!'

Alternatively, you can use the readlines() method to get a list of string values from the file, one string for each line of text:

# readlines() method: returns list of strings, one per line
with open('sonnet29.txt') as sonnet_file:
    sonnet_file.readlines()  # Returns list with each line as a string

['When, in disgrace with fortune and men's eyes,\n',
 ' I all alone beweep my  outcast state,\n',
 "And trouble deaf heaven with my bootless cries,\n",
 "And look upon myself and curse my fate,']

You can also iterate through the file line by line:

# Iterate through file line by line (memory efficient for large files)
with open('sonnet29.txt') as sonnet_file:
    for line in sonnet_file:  # File object is iterable
        print(line, end='')  # Print without extra newline

When, in disgrace with fortune and men's eyes,
I all alone beweep my outcast state,
And trouble deaf heaven with my bootless cries,
And look upon myself and curse my fate,

Writing to files

# Write to file: 'w' mode overwrites existing file
with open('bacon.txt', 'w') as bacon_file:  # 'w' = write mode
    bacon_file.write('Hello world!\n')  # Returns number of characters written

13

# Append to file: 'a' mode appends to existing file
with open('bacon.txt', 'a') as bacon_file:  # 'a' = append mode
    bacon_file.write('Bacon is not a vegetable.')

25

with open('bacon.txt') as bacon_file:
    content = bacon_file.read()

print(content)

Hello world!
Bacon is not a vegetable.

Relevant links

• File and directory Paths
• JSON and YAML
• 10 Essential File System Operations Every Developer Should Know
• open()
• print()