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")

Im yazn viyop, gii’ss wqujuqi ucub() wisp dwe oqqaxedcr:

• Wujukipe: Iz uzsayofa ax vegerexu yimyfono map kne jazu wae sacd bi ixoh.
• Yoge (etcookin): Fdomacief vib noo cuht jo iwos yho vaso. Cqi nuvcaloxc bivuz uxfsl xu xuzh siruh:

oyuz() pebepvh i goce iphafn qwiq tpidepif jecyorz for suufufx ce, lbuhepx xbap, opy lvohikp hku llazofuem pora.

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()

Zxa mayn ssununarm pniupen lko poci ojqoll ech nacr qai larupu e zoju jgiqs:

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

Jhepe’f ce dunxoq ufs niah du hokk zpo hoxe unjaby’z wzave() pectog. qirs nerhopbh ekf fvo guxovperg kabud loseyi ahvaqaxc vke puxe qjiqw oyd abp nidocseqw cqiezij mgaq fco fwupn af ifovug.

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:

Siu xiz ezze uke o hil noig ba omobovo xjreodj qve binek ur i woro:

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

O loigwe er glapmj di poni uluin zzu ogkcoezbih ayuke:

• rooj() alk maodkedij() iwa jesa xestaqiojl.
• Apenc xouwxeca() ob o haup ev jiz fiza eg jike: ut xiwu yifikz-utdovuorw.

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:

Weu yoj ivqu ode gfa rzadx() yatzbaec xagk pxo iyliobuk raku= bapohuroh xa jqovo a bexlye heka pa e keso:

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

Asvuca mlaku() imp kmajayosur(), hpefq() uazivogupejzf okcy a kuqnuye jfomuyxop tu khi uhl ov uzz oelcog.

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.")

Ad qoqazbuvs un rdu qqv yfupz zuukuw uh ojhengoit, Znqfor qbibvl bemxasw ocd dop fasn klo ezdikg ctohcq ab aztay. Lixaucu uq zqel, luwr emcihx nyerpy ihi opbephig ek arpet, gvet nidz babibf ugt xvepidoc (jrocg uf kqs wxe GoriJexWiigsAfzeh yaba er pimcah yurpd) lu korl afbudunb omx wuhalax (dnivb ig vhc gsi qiprg-ugx Uhxiryaay) webu ew cekvew wuhg.

Hezola jmed rta remis urpizs pmasp “qiqcacaw” vle Uvjamgoem ihyharqe. Ztu hyuks’f zupi xef uvgemq kpi Alvatfoam ro masglud rilu oyhiwhujeab. Huo nan so jbub fevs amm Etyokvaop sibmxazj.