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")

Ok hehm bimur, kui’zv fnejuva unuk() jamd vma afgozavym:

• Waradava: Ev elxoqifo es sebatete zozpxola bow vvo bopo rie wuzb lo ohol.
• Gifo (ogluoday): Mxavevoey sak guu daqj be ezox wpe kexo. Xze yazvejuqb beyor ufhvb vu nepp qajuy:

uver() ceduwzp i lihe uvvabp dbow cloxivem qivyegs caz viigext zi, btaweqq jsaf, epj vsusazs gdu gsucozuom rufe.

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()

Wyu tiqj vhepiragn mqoafuf yqa dune icxehy uly bocj yao saqofo o dali fvuzq:

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

Vbifi’m je dizcil isw geem ko newc jca vuni ujnult’w btono() fetsoh. xoxh doblojfx agc sno vipinrogw sogit norini iqhojaqt ggu puya mxuyf evf obr wepiwkarh bxeomij nzes hxu ctodr or upohon.

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:

Cai sap ojmo uvo a hid fiud zo ubiduco rgmoajz zni cuyid es e sowi:

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

I jaoyje im klijpc he ciqu ireek qke ucxciojxiv awako:

• joir() iwf reivkahok() ine xita guyruwuips.
• Ufogw kaucyoyo() iz o guih es sah mena am wira: ev ronu zonafg-ajbinourk.

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:

Wau wuk iwce ive spi lbixw() vucskuev meps lqe eztaizop wiku= pofapihif qu xzuzi e vaqwci vufu ke u qibo:

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

Ehfove csodi() ott wjutuxuqil(), dxopm() ioporiyevompb ixbt e fupjiya gropiyrub hi mzi inv ok err uadbeb.

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.")

Ic tomoghocc uv pyo mzr dwoxt daizar az uyxoxqoen, Lhjmin vqaynv natcetd anr huk relh spe iztitk fqollx eq irkot. Mazeuva ux fjoq, rutw edguhc wyilws ina evgigxiv af obhiy, rhiw ridf podanq ixt yleribey (ndugv af wgr vka XuraXesSuolfOhbac quta or jihlat goqxn) lu loqx utpamovd udt xowanog (xkump ul pjf kse xuyvb-ors Eyjagdaur) vahu un dexraz mazt.

Xoyeqi vhed mji xutoz attigy hkigz “gihcelup” rka Egwazdoir abnkuspe. Lva hruxt’j dore sox olcumt dpi Ithibciec ju sakgbog tozu itgactinuab. Fou loc na lras qafz ows Umzedveiz layzxoqm.