File Handling Python
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Files in Python represent sequences of bytes stored on disk for permanent storage. They can be opened in different modes like read, write, append etc using the open() function, which returns a file object. Common file operations include writing, reading, seeking to specific locations, and closing the file. The with statement is recommended for opening and closing files to ensure they are properly closed even if an exception occurs.
File Handling Python
- 1. Akhil Kaushik Asstt. Prof., CE Deptt., TIT Bhiwani File Handling
- 2. What is a File? • A file represents a sequence of bytes on disk, where a group of related data is stored. • File is ready-made structure. • File is created for permanent data storage (HDD). • Syntax: file_object = open("filename", "mode")
- 3. File Modes • r – opens a file in reading mode. • w – opens/ creates a file in writing mode. • x - opens a file for exclusive creation. If the file already exists, the operation fails. • a - opens a file in append mode. • t - opens in text mode. (default) • b - opens in binary mode. • + - opens a file for updating (reading and writing)
- 4. File Modes • In ‘append mode’, previous contents of file remain & we can write more data after it (if file exists). • In ‘write mode’, previous contents are cleared & user writes from scratch(if file exists). • A ‘Binary File’ is similar to text file. It deals with non-text files like images or executable files..
- 5. Opening Files in Python • Python has a built-in open() function to open a file. • This function returns a file object, also called a handle, as it is used to read or modify the file accordingly. • Ex: f = open("test.txt") #file in current directory • f = open("C:/Python38/README.txt") # specifying full path of file
- 6. Opening Files in Python • f = open(“raw.txt") # equivalent to 'r' or 'rt' • f = open(“raw.txt",'w') # write in text mode • f = open("img.png",'r+b') # read and write in binary mode • f= open(“raw.txt","w+") #read and write permissions
- 7. Create a Text File • f = open(“raw.txt","w+") • Here, f is a variable to open a file. • open() function is used here. • raw.txt is a text file that has name ‘raw’. • Permission is read and write. • If file does not exist, file will be created.
- 8. Writing in a File
- 9. Reading from a File • f = open(“raw.txt", 'r', encoding = 'utf-8') • f.read(4) # read the first 4 data • f.read(4) # read the next 4 data • f.read() # read in the rest till end of file • f.readline() #read individual lines of a file
- 10. Reading from a File
- 11. Reading from a File
- 12. Reading from a File Read the whole file line by line:
- 13. Random Access - File • There is no need to access the records of file sequentially. • To random access the files, there are 3 functions: • f.seek() • f.tell()
- 14. Random Access - Files • It is used to seek pointer position in file at specified byte. Its syntax is-> seek(offset, from = SEEK_SET) • Changes the file position to offset bytes, in reference to from (start, current, end). • f.tell() – It returns value of current position in file. The value is count from beginning of file. Its syntax- f.tell()
- 15. Other Functions • fileno() - Returns an integer number (file descriptor) of the file. • flush() – Flushes the write buffer of the file stream. • seekable() - Returns True if the file stream supports random access. • truncate(size=None) - Resizes the file stream to size bytes. If size is not specified, resizes to current location. • writable() - Returns True if the file stream can be written to.
- 16. Close a File • 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 close() method available in Python. • Python has a garbage collector to clean up unreferenced objects but we must not rely on it to close the file.
- 17. Close a File
- 18. Close a File • This method is not entirely safe. • 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.
- 19. Close a File • This way, we are guaranteeing that the file is properly closed even if an exception is raised that causes program flow to stop. • The best way to close a file is by using the with statement. • We don't need to explicitly call the close() method. It is done internally.
- 20. File Handling using Colab • Upload the file:- • Write from Colab:-
- 21. Akhil Kaushik [email protected] 9416910303 CONTACT ME AT: Akhil Kaushik [email protected] 9416910303 THANK YOU !!!