Python Tutorial: File Objects - Reading and Writing to Files
ฝัง
- เผยแพร่เมื่อ 28 เม.ย. 2016
- In this Python Tutorial, we will be learning how to read and write to files. You will likely come into contact with file objects at some point while using Python, so knowing how to read and write from them is extremely important. We will learn how to read and write from simple text files, open multiple files at once, and also how to copy image binary files. Let's get started.
The code from this video can be found at:
github.com/CoreyMSchafer/code...
Read more about opening in binary mode here:
docs.python.org/3/library/fun...
✅ Support My Channel Through Patreon:
/ coreyms
✅ Become a Channel Member:
/ @coreyms
✅ One-Time Contribution Through PayPal:
goo.gl/649HFY
✅ Cryptocurrency Donations:
Bitcoin Wallet - 3MPH8oY2EAgbLVy7RBMinwcBntggi7qeG3
Ethereum Wallet - 0x151649418616068fB46C3598083817101d3bCD33
Litecoin Wallet - MPvEBY5fxGkmPQgocfJbxP6EmTo5UUXMot
✅ Corey's Public Amazon Wishlist
a.co/inIyro1
✅ Equipment I Use and Books I Recommend:
www.amazon.com/shop/coreyschafer
▶️ You Can Find Me On:
My Website - coreyms.com/
My Second Channel - / coreymschafer
Facebook - / coreymschafer
Twitter - / coreymschafer
Instagram - / coreymschafer
#Python
![[UNCUT] รัฐสั่งหยุดปล่อยคลื่น! แต่หยุดพลังปะทุ “น้องหญิง” ไม่ได้ I คนดังนั่งเคลียร์](http://i.ytimg.com/vi/RmQh47eIiV0/mqdefault.jpg)
okay i'm at a point where i watch corey's videos just after waking up...
for fun.
U a anime boy?
Same here
i aspire to be this interested.
at the mo the only time i look up corey's videos is 3 hours before an exam when i timely realize that i have not ~bothered~ to learn a seemingly harmless but deadly aspect of the syllabus.
i wish XD
are u a masochist
No gimmicky loud background music or talking like he's some badass hacker...just clearly explained lessons that are easy to understand. Awesome work!
when ur actually a badass hacker, but act like a normal rational person
what tutorial have you seen where the guy doing it talks like a "baddass hacker" I want to watch that
@@stratosvagiannis5140Lul I’m also curious
My Notes for this video. You can comment out all of it and uncomment and run one function at a time to revise what Corey has taught us:
# While opening a file we can specify whether we are opening the file for 'reading', 'writing', 'reading & writing' or 'appending'
# If we don't specify anything, it defaults to 'reading'
# f = open('text.txt', 'w') # Opens a file for writing
# f = open('text.txt', 'r+') # Opens a file for reading & writing
# f = open('text.txt', 'a') # Opens a file for appending
# Opens a file for reading
f = open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r')
print(f.name) # Returns the name of the open file
print(f.closed) # Returns whether the file associated with the variable is closed
print(f.mode) # Returns the mode in which it was opened i.e. 'r', 'w', 'r+', 'a'
# All files opened using an open() command need to be closed explicitly after their use is complete. If this is not done , we can end up with leaks that cause us to run over the maximum allowed file descriptors on the system and our app can throw an error.
f.close()
# We can avoid this problem with a context manager as below
# The below 'with open()' command will close the file as soon as the code has finished running or an error is thrown
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# Code goes here
pass
# This produces the error "ValueError: I/O operation on closed file.""
# print(f.read())
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# This just reads all lines in the file
text_file_contents = text_file.read()
print(text_file_contents)
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# This returns a list that contains all lines in the file
text_file_contents = text_file.readlines()
print(text_file_contents)
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# This returns a line of text (not a list) at a time
# The first time we print .readline() it returns the first line
text_file_contents = text_file.readline()
print(text_file_contents)
# The second time we print .readline() it returns the second line
text_file_contents = text_file.readline()
print(text_file_contents)
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# This returns a line of text (not a list) at a time
# The first time we print .readline() it returns the first line
# Putting an 'end = '' in the return or print statement removes the newline between each result
text_file_contents = text_file.readline()
print(text_file_contents, end='')
# The second time we print .readline() it returns the second line
# Putting an 'end = '' in the return or print statement removes the newline between each result
text_file_contents = text_file.readline()
print(text_file_contents, end='')
# The above methods take a lot of storage as lines get stored in memory
# Iterating over lines in a file avoid this
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
for line in text_file:
print(line, end='')
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# Passing a number to the .read() command preads just that number of characters
# The first time this is run, a 10 characters will be read and printed
text_file_contents = text_file.read(10)
print(text_file_contents, end='') # It returns '#1) This is'
# The second time this is run, the next 10 characters will be read and printed
text_file_contents = text_file.read(10)
print(text_file_contents, end='') # '1) This is a test fi'
# The same line is extended (without introducing a new line or a new returned value)
# When we reach the end of the file, read just reads what is left and returns an empty string for the rest of it
text_file_contents = text_file.read(1000)
print(text_file_contents, end='')
# The below code will print out the entire code
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
size_to_read = 10
text_file_contents = text_file.read(size_to_read)
while len(text_file_contents) > 0:
print(text_file_contents, end='')
text_file_contents = text_file.read(size_to_read)
#
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
size_to_read = 10
text_file_contents = text_file.read(size_to_read)
while len(text_file_contents) > 0:
# The '#' symbol in the output marks the chunks that were printed in each iteration
print(text_file_contents, end='#')
text_file_contents = text_file.read(size_to_read)
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
size_to_read = 10
text_file_contents = text_file.read(size_to_read)
# The 'filename.tell()' returns the position of the file till where we've read until now
# This returns 10, since we've read 10 characters
print(text_file.tell())
text_file_contents = text_file.read(size_to_read)
# This returns 20, since we've read 10 more characters (10+10=20)
print(text_file.tell())
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
size_to_read = 10
# Reads the first 10 characters. Read position set to 10
text_file_contents = text_file.read(size_to_read)
print(text_file.tell()) # Prints 10
# Reads the next 10 characters. Read position set to 10+10=20
text_file_contents = text_file.read(size_to_read)
print(text_file.tell()) # Prints 20
# filename.seek() sets the read position to whatever character we set it to. Here set to 0.
text_file.seek(0) # Sets the read position to 0
print(text_file.tell()) # Prints 0
# Reads the first 10 characters. Read position set to 10
text_file_contents = text_file.read(size_to_read)
print(text_file.tell()) # Prints 10
# If we try to write to a file that is opened for reading. An error is produced.
# Error = 'io.UnsupportedOperation: not writable'
# with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
# text_file.write('Test')
# If a file with this name doesn't already exist. It will be created.
# If a file does exist, it will be overwritten
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text2.txt', 'w') as text_file:
text_file.write('Test')
# If you don't want to overwrite a file, use an 'append' setting by passing a lowercase a
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text2.txt', 'a') as text_file:
text_file.write('Test')
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text2.txt', 'w') as text_file:
text_file.write('Test') # File contains: 'Test'
# filename.seek(position) sets the write position to the number we pass in
text_file.seek(0)
# If we now write something. It will be written from the newly set position.
# It will overwrite anything in its path for as many characters it need to overwrite
text_file.write('LN') # File contains: 'LNst'.
# The first 2 characters from position 0 were overwritten because it was required
# Copying from one file to another, line by line
# This can't be done for image files. It shows an error. Invalid start byte. Copying an image file would require opening it in binary mode. We would be reading/writing bytes instead of text.
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
with open('C:/#Personal/Coding Projects/Proj1/Py edn/textcopy.txt', 'w') as copy_file:
for line in text_file:
copy_file.write(line)
# To read binary we change open(filename,'r') to open(filename, 'rb')
# To read binary we change open(filename,'w') to open(filename, 'wb')
# The below code with these changes, can copy an image file
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'rb') as text_file:
with open('C:/#Personal/Coding Projects/Proj1/Py edn/textcopy.txt', 'wb') as copy_file:
for line in text_file:
copy_file.write(line)
# Copying a file using chunks instead of line by line is better. This can be done by using the .read function we've studied above
with open('C:/#Personal/Coding Projects/Proj1/Py edn/text.txt', 'r') as text_file:
with open('C:/#Personal/Coding Projects/Proj1/Py edn/textcopy.txt', 'w') as copy_file:
chunk_size = 10
chunk = text_file.read(chunk_size)
while len(chunk) > 0:
copy_file.write(chunk)
chunk = text_file.read(chunk_size)
thanks for this ur a legend
Really, you`re a legend
Thx a lot, you saved me a bunch of time
Thanks alot! that was super helpful
Underrated Comment
Thank You Corey! You are a talented and gifted Tutor. I have watched over 50 python tutorials and yours are the best example of what I have found on TH-cam.
on 23:38, how does the last line of the while loop prevents infinite loop?
@@Laevatei1nn Once u read 100 elements, curser will move to 101. If we just read once outside the loop where u read only once and length does not decrease and loop run infinitely. if you read inside a loop, curser keeps moving after every loop and once if it finds no content to read u will get zero length data, so the loop breaks.
You are even better than the teachers in udemy . They don't know about being fluent.
I'm watching this tutorial meanwhile saw ur comment which is 5 yrs ago. He really explains things simply and easy to understand
Maximum efficiency and Ultimate mastery of teaching has been shown in this video! You present your tutorials like a rabbi who read the scripture his whole life! Magnificent!
Dude, I'm in love with your python series. Keep up the amazing work.
+Airth Thanks! I appreciate that. Glad you find them useful.
what version of python do you have in this video
please reply
So am I. There are good instructors of different languages. Corey is the guy in python. Thanks Corey.
The way this videos are systematically put together makes everything so easy to understand.
Watching your videos is so helpful and motivating .
Thank you Corey!
Yours are some of the best python tutorials I've found on TH-cam. No bs. Very well explained. Cheers mate
BEST PYTHON TUTORIALS!!!!!
ya trueee he is awesome
Really helpful explanation of read & writing to files. This was quick and succinct. Helped me understand a few things that others don't cover. I love how you covering just the right stuff.
You all tutorials are stright forward and cover all aspect of a specific topic. Thank you for this channel.
Simply the BEST python tutor ever...truly life saving! And the picture of your dog just made my day 100% better!
Huge thanks for all!!
You have the clearest, best explained videos on Python. Great job.
This video is so well explained. I’m a beginner and am able to follow everything perfectly!
Never saw a mentor like you before.
You are the one who teaches fellows like me for free.
Thank you so much sir.
Brilliant, A good teacher can make you remember concepts with ease. I am delighted to gain from your teachings. Thanks a ton.
These must be the classes from the Corey Schafer University.
Absolutely fantastic videos !
Probably the best and most detailed tutorials out there.
This was incrediby clear and useful. I actually started predicting what was going to happen not because it was obvious but because you explained it so well. Instant subscribe.
This chanel is something that i will watch all the python tutorials of, and will come back from time to time to refresh what i've learned, thank you.
Thank you so much!!!! Your video is extraordinary. You explain these concepts clearly and thoroughly, in a very engaging way with practical examples. You made me understand this topic very quickly. Thanks again!
This really helped me understand how to read and write to files. Thank you for your time and expertise.
Very clean and too the point tutorial. Thanks for this easy to grab explanation. I'm quite comfortable now as far as basic file operations are concerned.
although I am discovering this 8 years after I still find it very awesome. Keep up the good work man
Man , these videos are Really good.. The author focused on actual real time use cases and tutorial makes so much sense.. Great Job
2 years Later: It's still relevant God damn it !! Thanks Corey
Thank you Corey for your time and effort. Keep spreading the knowledge.
Absolute killer tutorial! Thank you! I've subscribed. I'm in Lambda School learning python and this cleared up a lot. I appreciate it.
Your puppy is ADORABLE!! Thanks for the video
Thank you! You made the video interesting whilst keeping it simple, I am a beginner and this has helped a lot.
these are better than my 2 hours lectures... My professor sucks so much at teaching python. These are amazing and a life saver!
Have u graduated already?
You always hit the depth level I need on specifics.
Hey man you made school much quicker and easier for me, thank you!
Now I'm in a confusion that weather the creator of python or its this guy, "Corey Schafer" , made python so simple. Thank you sir for your awesome explanation
This man deserves a knighthood.
In the name of the Warrior I charge you Ser Corey Schafer to be brave.
In the name of the Father I charge you to be just.
In the name of the teacher I charge you to educate the masses.
In the name.....
Arise Ser Corey Schafer:)
user_nickname = "This man"
user_title = " Ser "
user_name = "Corey Schafer "
action_prog1 = "to be brave"
action_prog2 = "to be just"
action_prog3 = "to educate the masses"
prize = "a knighthood"
supernatural_being1 = "the Warrior"
supernatural_being2 = "the Father"
important_person = "the teacher"
speech = user_nickname + " deserves " + prize + ".
" + "In the name of " + supernatural_being1 + " I charge you " + user_title + user_name + action_prog1 +".
" + "In the name of " + supernatural_being2 + " I charge you " + action_prog2 +".
" + "In the name of " + important_person + " I charge you " + action_prog3 +".
" + "In the name.....
" + "Arise" + user_title + user_name + ":)"
print(speech)
?
@@user-ec5oc5fb7b I guess that works
yeah in the name of......
Ur name looks little bit girly so did you forget in the name of husband
i think i got enough to get started on my first python project but gunna keep watching one a day because they are soooo good!
Great tutorials Corey...Thanks a lot for making all this so simple
Corey, I am discovering me a fan of your great channel!! Thanks a lot, man
You're a truly talented teacher. Better than any online course I've tried so far.
Thanks! I appreciate that.
Wow. I've been trying to learn certain concepts in python for a while now and I've come to the conclusion that your videos are beyond amazing and super helpful. literally couldn't be more grateful
I rarely comment a video, but thank you Corey. You earn yourself a subscriber for life 😊.
Sir you make the best tutorials of python! I'm sure not even the paid stuff can beat this.
Thank you very much sir for putting so much effort in helping other by sharing your knowledge.
Wow. This channel is going to be an epic for Python learning. Every topic covers the crux of the items cleverly
I'm learning so much from you tutorials without getting frustrated ,thank you so much !
Very simple to understand and just filtering out the important bits alone! If you do have a dedicated tutorial in udemey, I would love to subscribe!
Keep creating Sir Corey! :P :D
my teachers can learn a lot from you
Very detailed, an excellent example for what a tutorial should look like 👍 keep being so awesome
Amazing.. am loving Python even more now ! Please dd more tutorials to Files on files like reading from IO, memory, csv files, or extracting data from unstructured format .
This is so fkng good, tkx for the content, srly, well explained and covers a lot of ground, loved it.
You're a blessing, thank you
i thought i know how to read and write file, after watching this series i now know how to write and read awesome files. thanks so much
Thank you so much Corey. You are the best teacher I have ever seen.
I agree with Airth. Your python series is awesome. Your videos are great. I think its the depth you go into, the many different ways to do it, and the way you should do it. Oh and so much "energy" and "flow" in the videos.
you are the best when teaching python. period.
Thanks!
Thanks for explaining everything in such a simple manner
I really admire you, how you can made things so simple.
finally someone that explains it properly! Thank you :)
*** Thanx Corey - Excellent Video. Nicely spoken, great pace, very informative and easily understandable.
Great work - thank you! :¬)
Best python video tutorial on the Internet, bar none.
Don't @ me.
This is a great tutorial, You simplify complex topics and make it simple to understand
This man deserves Computer Science professor of MIT
Love your Python (and other) videos - some of the best coding tutorials on TH-cam. Very clear, detailed, in-depth explanations that get right to the point. Great work!
Ideas for future tutorials:
-Much more on classes, including composition, polymorphism, when to use classes vs other data structures, etc.
-Enums and when to use them (introduced recently in Python)
-Examples of when to choose different data structures and how to implement each.
- Oauth and working with APIs through Python
-PDB / debugging
-Testing web apps
-Selenium and Python
-Beautiful Soup
-Pytest
-Pylint
-TDD
-Encapsulation / structuring code in python effectively
-Advanced namespaces / modules / packages
-Flask (advanced or in-depth, eg explaining the app context and how working with Flask blueprints is different from the usual modules and if ‘__name__’ == ‘__main__’
- Intermediate/ Advanced object oriented programming
- Refactoring and code smells
- Functional programming
- Advanced Sublime Text
- Workflow, eg syncing dev environments across different platforms, version control for dotfiles, etc.
- Productivity tips
- Design patterns
- Medium/low-level networking and web programming with Python (understanding HTML headers, session objects / cookies, HTTP protocol, servers, AJAX and REST APIs, etc.
- Setting up a personal web server, mail server, file server, owncloud, etc.
- Executing JavaScript with Python
- Setting up a LAN / basic home networking
- Scripting and automation tips/ideas/anything
- MongoAlchemy and/or Pymongo and/or SQLAlchemy
- Building a web app with Python/Flask backend and JavaScript/Angular frontend
- Advanced regular expressions (maybe covered in your newest video)-e.g., escaping regex strings
- String templating, text replacement, etc.
- Collections module
- Modules that are useful or should be in the standard library but are not
- Advanced / in-depth primitive operations, e.g. string and dict methods.
Thank you!
this was awesome ! waiting for the more advances topics that you suggested !!!
Hello, Corey, You are the best. I started learning Python recently and your videos are very helpful. Thanks.
my brain has exploded
awesome tutorial :)
+Pravesh Jangra Thanks! Glad you enjoyed it.
Love the turtorials and your dog ! So cute !!!
My brother , Thank you ! You are a great educator of our time !!!!
How would I read/print a random line from the file
Use f.readline() in a loop (or for line in f: ) to make a list of all the lines and then use random.choice() to select a random element of that list
Thx for vids signed up to became your patron!
BTW, what about that tmp files and in memory files vid, is it on your channel?
Thanks, Alex! I really appreciate that. I haven't recorded the tmp and in-memory files video yet, but I still plan on putting one together in the near future after I get some other videos in my list finished up and published.
Thanks again!
Looking forward :)
I've just come across this and you are about to become my saviour because I'm about 10 hours behind on my controlled assessment and have no idea what I'm doing
Your tutorials are the best! So much useful information.
Thanks a lot!
16:10 Careful! File contents(if exists) are erased the moment it's opened in write mode.
U r experienced
too late, deleted my bank account passwords
"...it didn't delete the rest of the content" HAHA
No questions, just infinite thanks. Subscribed and recommended.
this is the content i have been searching for a month now. damn
How do I write and read a file simultaneously .I tried to do but after every read operation its simultaneously writing the same content the no of times i run the prog which is not what i want .Please help !! Thank you !
Well. Hope this isn't too late 😅
But you need to control the file pointer on the open file object, when you open a file in r+ or w+ mode the file pointer starts from the top of the file (0) so you'll need to get it to the end of the file before writing new data
Great tuts. I assume this is for python 3? I tried to do this in 2.7 and it doesn't seem to like the syntax with the "end". I guess I should start transition to 3. Overall like your style of teaching.
Edit- I got it to work if in python 2.7, you have do an import -> from __future__ import print_function
Sorry for the late reply. Yes, this is Python 3. It took me a long time to transition over too, but since it is the recommended version now it is a good idea to switch over if possible.
The same thing happened to me lmao. I checked my version and it is 3.6. Now im totally lost. I can use it in IDLE but it failed in Sublime
I finally found someone who makes sense. Corey, this is amazing thank you!
Thank you Corey! Very cool lesson! Clear and useful 💛
More videos please!!
PLEASE POST SOME TUTORIAL ON NETWORK PROGRAMMING USING PYTHON....THANKS IN ADVANCE !!
ARe you an ethical hacker?
Udemy has just the right one for you "ON NETWORK PROGRAMMING USING PYTHON." they are very affordable too.
th-cam.com/video/Lbfe3-v7yE0/w-d-xo.html
This is best youtube channel to learn python!!
What an excellent playlist. Thank you very much Mr Corey.
for line in f:
how does it take in one line like we havent specified anything
line why doesnt line iterate through each character .
how does it iterate through each line
can someone please help me? :)
yes same doubt buddy!!!!!
@@vaibhavdumaga7229 Same issue here. But I think it is in-built and so the for-loop function automatically knows. From documentation, it says that some file objects are iterable, meaning when used in a loop, it automatically "knows" how to go to the next item in the file object.Don't fully understand, but it seems to be in built so it's automatic. See for yourself here under iterable: docs.python.org/3/glossary.html#term-iterable
OMG THS IS M FAVURIT VEDIO EVVRR
sorry jude thats wrong
same
I can't stop watching these tutorials! Thanks, man!
Thanks! I'm happy to hear you're finding them useful.
You are the best teacher! Excellent videos. Thank you!
Who's here from UoPeople?
Yo.... this is much simpler in python than in java
Hi Corey, Fantastic Video..very clear with your explanation..Than you so much for your efforts on making this video..Love to watch your series..
Thanks Corey! Very informative and I plan on seeing more! I owe you one...
Thumbs up for puppy pic
Thankyou I am able to Tweek this into my file today as an option for the user to read rules and save their text to be used later. Thumbs up :)
respected sir you are a legend one of the finest tutorial til date i wish i had a teacher like you to guide me on coding thank you sir for your help
Awesome tutorial Corey! really enjoyed that (thumbs up).
Great tutorials.....Very useful and elaborated...Thanks for making them...
I appreciate your excellent effort, which saved me both time and frustration!! I'll spread the word:)
Your explanations and method is great. Thank you so much for your great tutorials.
really great video, cleared all my concepts, thanks a ton !!!