Python provides inbuilt functions for creating, writing and reading files. There are two types of files that can be handled in python, normal text files and binary files (written in binary language, 0s and 1s).
Note: To know more about file handling click here .
Access modes govern the type of operations possible in the opened file. It refers to how the file will be used once it’s opened. These modes also define the location of the File Handle in the file. File handle is like a cursor, which defines from where the data has to be read or written in the file. Different access modes for reading a file are –
Note: To know more about access mode click here .
It is done using the open() function. No module is required to be imported for this function. Syntax:
File_object = open(r"File_Name", "Access_Mode")
The file should exist in the same directory as the python program file else, full address of the file should be written on place of filename. Note: The r is placed before filename to prevent the characters in filename string to be treated as special character. For example, if there is \temp in the file address, then \t is treated as the tab character and error is raised of invalid address. The r makes the string raw, that is, it tells that the string is without any special characters. The r can be ignored if the file is in same directory and address is not being placed.
Here, file1 is created as object for MyFile1 and file2 as object for MyFile2.
close() function closes the file and frees the memory space acquired by that file. It is used at the time when the file is no longer needed or if it is to be opened in a different file mode. Syntax:
File_object.close()
There are two ways to write in a file.
File_object.write(str1)
File_object.writelines(L) for L = [str1, str2, str3]
Note: ‘\n’ is treated as a special character of two bytes. Example:
Output:
Hello This is Delhi This is Paris This is London
When the file is opened in append mode, the handle is positioned at the end of the file. The data being written will be inserted at the end, after the existing data. Let’s see the below example to clarify the difference between write mode and append mode.
Output:
Output of Readlines after appending This is Delhi This is Paris This is London Today Output of Readlines after writing Tomorrow
with statement in Python is used in exception handling to make the code cleaner and much more readable. It simplifies the management of common resources like file streams. Unlike the above implementations, there is no need to call file.close() when using with statement. The with statement itself ensures proper acquisition and release of resources. Syntax:
with open filename as file:
Output:
Hello This is Delhi This is Paris This is London
Note: To know more about with statement click here.
To write to a file in Python using a for statement, you can follow these steps:
Open the file using the open() function with the appropriate mode (‘w’ for writing).
Use the for statement to loop over the data you want to write to the file.
Use the file object’s write() method to write the data to the file.
Close the file using the file object’s close() method.
In this example, the file is opened for writing using the with open(‘file.txt’, ‘w’) as f statement. The data to be written is stored in a list called data. The for statement is used to loop over each line of data in the list. The f.write(line + ‘\n’) statement writes each line of data to the file with a newline character (\n) at the end. Finally, the file is automatically closed when the with block ends.
This is the first line This is the second line This is the third line
Approach:
The code opens a file called file.txt in write mode using a with block to ensure the file is properly closed when the block ends. It defines a list of strings called data that represents the lines to be written to the file. The code then uses a for loop to iterate through each string in data, and writes each string to the file using the write() method. The code appends a newline character to each string to ensure that each string is written on a new line in the file. The code optionally prints each string as it is written to the file.
Time Complexity:
Both the original code and the alternative code have a time complexity of O(n), where n is the number of lines to be written to the file. This is because both codes need to iterate through each line in the data list to write it to the file.
Space Complexity:
The original code and the alternative code have the same space complexity of O(n), where n is the number of lines to be written to the file. This is because both codes need to create a list of strings that represent the lines to be written to the file.
The write() method in Python is used to write data to a file. It takes a string argument and appends it to the end of the file’s content. If the file doesn’t exist, it creates a new file.
with open('file.txt', 'w') as file: file.write('Hello, World!')
Use the write() method with a newline character (\n) to write a line to a file.
with open('file.txt', 'w') as file: file.write('This is a line.\n')
Convert numbers to strings and use the write() method to write them to a file.
with open('numbers.txt', 'w') as file:
file.write('123\n456\n789\n')
Convert list elements to strings, join them if needed, and write to a file using the write() method.
data = ['apple', 'banana', 'cherry']
with open('fruits.txt', 'w') as file:
file.write('\n'.join(data) + '\n')
You create a file in Python by opening it with the ‘w’ mode in open() function. If the file doesn’t exist, Python will create it.
with open('new_file.txt', 'w') as file:
file.write('Content of the new file.')