Reading and Writing Files: Handling Text and Data Efficiently
Reading from a File
To start reading a file, you first need to open it in the appropriate mode. Here's how you can open and read from a file:
python9123456file = open("greetings.txt", "r")print(file.read()) # Output:# Hello, world!# Salut!# Hola!file.close()
Reading Specific Characters
You can also read a specific number of characters by passing a numeric argument to the read method:
python9123file = open("greetings.txt", "r")print(file.read(10)) # Output: Hello, worfile.close()
Reading Line by Line
To read a file line by line, you can use a loop along with the readline()
or readlines()
methods. The readline()
method returns a string for each line, while readlines() returns a list of all lines:
python91234file = open("greetings.txt", "r") # ['Hello, world!\n', 'Salut!\n']print(file.readline()) # Output: Hello, world!print(file.readline()) # Output: Salut!file.close()
For more efficient line-by-line reading without loading the entire file into memory, use a for
loop with readlines()
:
python912345678file = open("greetings.txt", "r")for line in file.readlines():print(line, end="") # The `end=""` argument prevents adding extra line breaks# Output:# Hello, world!# Salut!# Hola!file.close()
Writing to a File
To write data to a file, you should open it in write mode ('w'). Only strings can be passed to the write() method.
python9123file = open("greetings.txt", "w")file.write("Bonjour!")file.close()
Note
The writing mode overwrites the existing file content.
In this case, any existing data in "greetings.txt" will be replaced with "Bonjour!"
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