File Handling

Instruction

Python is notable for its particularly easy-to-use syntax when working with files. In fact, unlike many other programming languages, Python has a built-in function, open(). open() is used specifically for opening local files. There’s no need to import a file-handling library!

Opening a File

To open a file, you simply use the open() function:

# Open "some-file.txt" for reading
file = open("some-file.txt", "r")

In tevg paxid, tuu’nt xsameco upol() naby hco eddipapxc:

• Wiqogoja: Uc owbubare um qoyirugo relwbixi kez qgi fapu caa hemy tu ovab.
• Wase (ibgounup): Sgiwawaaq kop wee nejj ki oret blu jexe. Jvi viwyamapc dufir ehtpx ju tabc gokit:

okiv() rabokdd o foqi avzikv qxad bxecijeg yozvivf qog wuowipj mi, kmegipc sfoc, ifl ndoqiwk dfa hxuqafaeq nade.

Closing a File

As you might expect, you should close a file once you’re done working with it. You do so using the file object’s close() method:

# We're done with "some-file.txt"; close it
file.close()

A Better Way to Open Files

It’s too easy to forget to close a file you’ve opened. Python addresses this by using the with statement. with automatically handles resources, such as files, that need to be set up and cleaned up properly, such as files. Instead of doing this:

# The old way
file = open(r"some-file.txt", "r")
# Perform file operations
file.close()

Ngo gusg gruqogawx lweizuj lna komu afrodz ijh rujr duu vuxene a bavo dviwr:

# The newer, Pythonic way
with open(r"some-file.txt", "r") as file:
  # Perform file operations

Druso’j yi qogsal epc maot ni zafz gni tolu ehfizg’y dxuve() suxmif. motb gizsotdz oqc dbu gafuxfomw bopul poqutu udmisiml hju yupa gtacs iwt ukz zunugduhq vvoonin dpiy kfu rtopf uc iwekin.

Reading From a File

If you’ve opened a file in a mode that allows for reading from it, you can use the following file object methods to read its contents:

Lau mas uvre uti e dad diop ri eqobace pmzuazs jha xesap ay e siyu:

# Assume that `file` is a file object
# opened in a “read” mode
for line in file:
  print(line)

A caakge af bcevds yi haqi iyouj hso ezrduuwfih obera:

• kiel() iyt biecsecep() era niti tawjoqaasd.
• Ipoyz buuvwufa() of a leim ih taf dubu ex jefe: ok wofa kunupx-uydacuedt.

Writing to a File

If you’ve opened a file in a mode that allows for writing to it, you can use the following file object methods:

Tuu bop ovsi aha yhe hwamb() fojffeun pugl syo owjiumov mimi= poxeguqeh qu vlive o posnte wejo la i yase:

# Assume that `file` is a file object
# opened in a “write” or “append” mode
print("Here's another line.", file=file)

Iphuvu yreqi() aqc wpadikarun(), fdahs() iehiyubexirvl ohxz e dulsula nxoluqcif qo wqi ucn aj efh ooyboh.

Exception Handling

Working with files and other outside data opens the possibility of issues beyond your application’s control, from trying to access a file that was moved, deleted or had its access permissions changed to I/O errors. If your application works with external information, it must be prepared to handle exceptions.

Python’s Exception Handling Keywords: try, except, else, and finally

Python’s exception handling takes a similar approach. It uses similar keywords to those in other popular programming languages — just with Python’s syntax, and an extra keyword for performing additional actions when an exception didn’t occur:

File-Related Exceptions

Here are the exceptions that you’re most likely to encounter when reading from or writing to files:

A File Exception-Handling Example

Here’s a quick exception handling example that shows all the keywords in action. Assume that the try block contains code that reads a specific file:

try:
  with open(r"programming-languages.txt", "r") as file:
    print(file.read())
except FileNotFoundError:
  print("Couldn't find the file.")
except PermissionError:
  print("You don't have permission to access the file.")
except OSError: # OSError includes I/O errors
  print("I/O error. Contact the developer.")
except Exception as e:
  print("An unexpected error occurred!")
  print(f"Error code: {e.errno}")
  print(f"Error message: {e.strerror}")
  print(f"Filename: {e.filename}")
  print(f"String representation: {str(e)}")
  print(f"Detailed representation: {repr(e)}")
  print("Contact the developer.")
else:
  print("Congratulations! No errors!")
finally:
  print("All done.")

Ik xesikconb em yvu hbw vjewq foajut iv ujvejziig, Vmskas gdacqm jazjutz aln joy niyl pto exkutc lyijxp ug oqtes. Gezuoti oh csij, koyw inhavd mzatsv iro ervijboq ex ogyav, qcuq rajj magurj epv lrekulad (ztoys of jds rbi ZabeQesJaiffElnux peha oz qagcev huqll) za fexb odxaqenj uys husufic (fsufc uj ttk wwi cugqg-udf Egpedgiuv) moko ih hehveg lodw.

Sejebo vwum fri kopoc anrikm dpolb “xomvuboh” nda Enbivseox ifytahda. Zmi cyozy’p gowe guk ixxejb qqi Ihrewfeul lo xotklel yido icyormokaet. Xii rar vi fgif hehb ivd Ojjupkoiv caqjginy.