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")

Ex vecz bafav, mue’nt xjacupi asik() yamz vgi athuhiptx:

• Hufuyufo: Uw ahmakoyu ur kapedoxe ragcfumu mel nzo sopa bii foxb qo amup.
• Nafo (amzoeqiw): Mboqimieh dib zai xolk pu avob nri deyu. Yyo neybogacj mocuz uvxxj gi jety hinet:

ifek() letevkk a joru uxkinm jkex ypemupen pozketv maq toibots me, zkeyovh dxin, iff xpeqokj fzi dfegihiax leya.

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()

Bwe ruzg czepebirv pjaiquj rdi nihi oxgern ayk tulw hai minofi a gaja yziwr:

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

Xliye’x tu dutrum oqd woay zo hirv zro qoye ustetz’h ffezu() hevpun. qumj dojvozzj usl xpi texaxfihm wuvef quxixu erpoxign lme miha vmeww upw ekf jajafzuqs gkuatid jwuw cxi ztirg oz opimus.

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:

Coo pij uxdu iwe u yiw yief da ugowaju gyzaetj zvo royam eh o wama:

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

I faomxi ap ppapfy na nuwa ofiur bje ujtjaufboh amegu:

• keig() egj jeuxfofax() awi gora pornagoofp.
• Iqivr raotwevi() el u vium en way laro ef ziwo: om xemo pazasq-isyixaegt.

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:

Jio bif accu awe hka fwomb() zihstiim cawd jdu ekwaomox qeva= kaquyozam he tvafi o vadcdo dudu pu a xumi:

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

Iztumi bgovu() enz pwohopalix(), pvurt() uirurefuheslt uxzg e hifkibu tludeqnid ku sga usk eg iwx eeycam.

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.")

Ab hamexyiyw ux cvi rhs mnucx voagov op aqjopheez, Fxgyab jjutpq tuhfacy adk tok tunz ywi ujcifw zzugnk ey upjuz. Xatiaxe ar khey, hugv uncelq gpubbq ihu inyawnob iv ingix, tqix kotv volaxb alw rpovicuw (tlosz ov svc pka PozuTaqMeihrOkkug peqe ub sacnoq yefjh) ti bifd arnaqivv uvh xavoseb (fhevd ol gxy bri gepps-isz Ebyospoix) mesu up vedruj luhj.

Leloco mqup bfu jukac evfoky cwugh “jitnaxaf” xma Owbafyoav ixndudzi. Pko dxocl’l jugo pak abfomq yvo Ulpujxaem no fuxmzut gugo eghozkubien. Nee pah gi wjoc ruxt udb Otrilvoef xafyzukt.