CS50P - Lecture 6 - File I/O

[@shafialanower3820]

I am not the biggest fan of coding but this guy's passion is enough to make me give it a go

[@manalbutt1332]

That's Great!

[@marticus9170]

This is probably the most intensive lecture of the course so far (I haven't watched the next ones yet). It's a lot of information, I'll have to watch the video 3 or 4 times to process all the information properly haha.

[@tryhardjak]

ha that's what I'm doing lol

[@marticus9170]

@@tryhardjak Good luck bro :)

[@tryhardjak]

@@marticus9170thanks man, rn i'm stalling on the last project and instead doing leetcode qs :)

[@Kiriletto]

That was dense

[@captaingaz8705]

Prior to taking cs50 course I couldn't get past week 1, had difficulty understanding problem-solving logic behind loops and functions, This course has been a breeze of fresh air, thanks to cs50 and David's eccentric enthusiasm for teaching ^^

[@BullCraftMaxx]

Yes I love the significantly slower pace on this course!

[@TanzidTushar]

with open("students.csv","a",newline="") as file: use this line for opening the file in order to practice writer method unless you will get extra line which will generate buggy csv file . I was facing the problem and found this solution in stack overflow and it magically worked for me .

[@anatoliy4360]

I searched right this comment. Thanks :)

[@ifeanyiojji]

Thanks dude struggle with this 1:18:22

[@DarkAcademyUniversity]

🤗🤗🤗

[@Lukytazcuervo]

copilot said the same as you

[@minhkhoango1256]

just what I needed, thanks man

[@atomicsprinkles5423]

I've been trying to learn python for awhile now but I don't have access to a lot of courses because of my age, this really broke the barrier and helped me decide to fully jump into the waters and try and make a career from it. Thank you so much

[@davidjmalan]

Glad you found the course helpful!

[@Tweston3ny]

❤

[@HovJigga]

Hows your path currently going. I'd love to hear qhat you did after and where it took you

[@ТатьянаЛарина-ш8у]

Дуже гарні курси. Це здорово, коли є такі викладачі.

[@ProfShibe]

fr

[@banka990]

You make by far the best and most detailed and up to date courses out there. And you are the best teacher, prof. Malan! I would really appreciate if you decided to make a detailed CS50 Django course, as a sequel to this one that builds gradually, and you to be the teacher. I'm familiar with the CS50W, but it looks more like an overview than a course you can learn from scratch and become fluent after finishing. Thank you!

[@penteronto]

If someone is wondering what's the quick fix to problem at 59:20 it's that: name, home = line.rstrip().split( ',' , 1) split accepts two parameters, first is the separator and the second is number of times to split the text because i passed 1 into the function that means that line will be split based on the first comma only. Note that it won't work if you'd have more columns than two so it's generally a bad practice

[@floki0407]

its will print harry is in "Number Four, Privet Drive" instead of harry is in Number Four, Privet Drive

[@All4You22]

​@@floki0407 Don't use quotation then

[@patryk5654]

@@floki0407 that's not true it will print Number Four, Privet Drive

[@sayori3939]

Yes file I/O the thing you look up 70 times a day because you never memorize the syntax

[@sayori3939]

That was a lot of information 😖😖

[@zakariyahussain1607]

@@sayori3939 bruv

[@Adel-pn2up]

😂😂😂fact

[@yoo8157]

happening now 😂

[@mattmurdock6352]

​@@yoo8157ah all that indices makes me crazy

[@yousefali755]

Thanks for your work D/ Daivad and all harvard ! .. a student from Egypt ❤

[@energy-sapped6184]

Great to find someone from my country here too❤

[@Sobrietyyy]

There is no way the students are introduced to this for the first time and even be able to grasp the concept good enough to be able to ask questions about it. I am watching it hoping to get familiar with the concepts and not trying to fully understand before moving on to the exercises since anyone who is challenged with the exercises will have to either come back to this video or search through documentations on how to get stuff done. I'd suggest you to have a go on the exercises even if you don't feel confident since as I've mentioned chances are you are gonna be doing a lot of research anyways before you can actually complete the exercise.

[@rengoodman1656]

really helpful tip

[@Madvincul]

Where do you find exercises? I can understand what he is doing when he is writing the code, but I could NEVER come up with a single line by my own.

[@adann99]

@@Madvincul If youre find cs50 problem sets then just search "cs50P" on google and youll see the lecture's videos and the problems sets with it

[@Sobrietyyy]

@@Madvincul thats why you should try before you get help, but i will admit this one's a tough one. Exercises are located once you complete the required integration of vscode workspace which i belive instructed on the website. All the course videos have exercises try completing them before you move on to the next video

[@Alexchii]

They're Harward students, though.

[@decrepit1]

This lecture and the libraries one, the most enjoyable so far

[@oyekanmibamidele6196]

I'm in Love with coding just because of Jay, the man of the game!

[@adeoyedavid2991]

I just love this guy and this course making programming easy .

[@yqhanliving]

As good and passionate as always. Thanks cs50 team!

[@cleidysbrooks]

Good Morning Python Family. I late.. David is the best! Thanks 👍

[@manalbutt1332]

Good Morning. Shouldn't it be a Great morning?

[@epitomeofrafsan]

if at 1:04:36 it shows ValueError too many values to unpack, you can use quotechar= ' " ' in the csv.reader function to specify that the quotes represent as a single value, so like this: reader = csv.reader(file, quotechar= ' " ')

[@RomiVa...]

you need to put the Harry's home address in double quotation like this Harry,"Number four, Privet Drive" Ron,The Burrow Draco,Malfoy Manor then it will work all right.

[@_schemaki_]

00:00:00 - Introduction 00:00:24 - File I/O 00:01:17 - lists 00:05:54 - open 00:13:55 - with 00:21:39 - sorted 00:29:31 - Comma-Separated Values 00:46:37 - Sort Keys 00:53:01 - Lambda Functions 00:57:13 - csv Library 01:02:17 - csv.reader 01:07:49 - csv.DictReader 01:14:05 - csv.writer 01:16:28 - csv.DictWriter 01:23:00 - Images, PIL library 01:31:42 - Conclusion

[@DarkAcademyUniversity]

"I make my life more complicated for a moment" 😅 love it!

[@nimbabul8384]

guys, please, don’t be lazy to press the like button. There are very few such useful videos on KZbin

[@jacksonmadison9994]

I never press the like button on any video, because it saves every liked video to a playlist and I don’t like seeing an unwanted playlist clogging up my screen

[@smileorcry7204]

​@@jacksonmadison9994same reason.but I have liked this video.

[@LuisAntonio-ql2tg]

Thanks David for your passion to teach!

[@SaidaYengui]

Amazing really good job David!

[@Someone-yl8sb]

This course is loaded with information damn

[@labheshsonawane7076]

I have a doubt in CSV file handling. So, if we use Comma separated values i.e. CSV file to store multidimensional data, then why do we need the .split( "," ) method to separate these values again? the same thing could be done in Txt file then using .strip( "," ) at 01:01:03 ? The same program runs properly if I just put students.txt file with same data as Csv file used here. then why do we need whole new type of file Csv??

[@anishagiri21m]

I think you need to complete this course first after the python lecture in cs50, then continue with the rest of the cs50. It makes so much sense now that I have already completed cs50.

[@Safar_Galimzyanov]

1:05:00 This approach doesnt work for me for some reason. I get the same error as before: ValueError too manu values to unpack. Ok, it expects commas "" in the csv line

[@derekloyer]

You already solved it, but to make it clear for anyone else looking for it - in the .csv file, he put " " around Number Four, Privet Drive so it looks like. Harry,"Number Four, Privet Drive" telling the CSV functions to not treat text inside the quotes as a separated value.

[@bryanflanigan5439]

Had the same issue…thanks!

[@Safar_Galimzyanov]

@@bryanflanigan5439 my pleasure!

[@Gab-jj5su]

I was going crazy with this error, thanks to your comments I figured it out. Very helpful

[@andrejg3086]

@@derekloyer Thanks dude, I was also wondering where this error comes from.

[@MaziarHeidari-i4e]

Great team. Thanks

[@mahipalmahato7648]

5:35 8:20 10:36 13:01 15:32 18:31 19:14 20:37 23:25 24:53 25:58 26:50 32:44 36:41 39:23 41:32 45:06 46:08 49:25 50:00

[@amandaflood]

On lambda functions, the one given is very simple - if it were a separate function it would only take up one line of code. What happens if you need to do more to the parameter before returning a value - the equivalent of a few lines of work? Would this still work as a lambda function - and if so how would you write it - or is lambda only used for the simplest cases?

[@mesaber86]

"The main difference between lambda function and other functions defined using def keyword is that, we cannot use multiple statements inside a lambda function and allowed statements are also very limited inside lambda statements. Using lambda functions to do complex operations may affect the readability of the code."

[@iZusi]

Beautiful lecture! So detailed and easy to grasp!

[@bashehu]

I came to peek on the lecture and ended up watching all 😂

[@vaibhavagarwal1479]

this class for me byfar was the hardest code was as friendly as always

[@mmulisha1022]

One note in here, is if you didn't have the for thought to ensure the capitalization of the names when passed into the .txt or .csv file, the sorted function also sorts by capitalization. You can clear this up by adding .capitalize(). 23:56

[@bigbro1815]

Thanks David

[@wesleycao5506]

students = {} with open("students.csv", "r") as file: for line in file: name, house = line.rstrip().split(",") students[name] = house #sort by key for name in sorted(students): print(f"{name} is in {students[name]}") #sort by value for name in dict(sorted(students.items(), key=lambda item:item[1])): print(f"{name} is in {students[name]}")

[@patryk5654]

1:18:21 it doesn't work for me. I have to specify new line: with open("students.csv", "a", newline="") as file. When I don't, it will use and write data every other row. But when I did it on cs50 web environment newline was automaticly = ""

[@BhavyamMittal-gi3jn]

when I try to code the files costume1.gif and costume2.gif, I have a problem "an error occurred while loading the image". Are there anyone who have the same problem as me, can you give me an instruction to fix this, please.

[@fahadahmedmahdi5137]

yap bro same case also happened for me

[@faizaabdulrasheed9680]

Same bro just completed this lecture and not able to do upload images to vs code. Did you get the solution yet??

[@andrejg3086]

@@faizaabdulrasheed9680 I had that error because of the antivirus program. Only after disabling it was I able to upload those images.

[@HairoHeria]

have the same problem even right now

[@andrejg3086]

@@HairoHeria In my case, the antivirus program (Kaspersky) was blocking the loading of those images. It was only when I turned it off that they loaded.

[@sushmasingh9040]

can't we do this in 46:44 with open("cs50_ch6.csv") as f: for l in sorted(f): name,house= l.rstrip().split(",") print(f"{name} is {house}") why do everything

[@grishmakhanal1655]

yes it will work you just did it in a different format

[@abanaru]

At the inverse sorted question (25:42), first thing which came to my mind was to use slicing, which was discussed in a previous chapter. Then line 7 would become: for name in sorted(names)[::-1]:

[@expect_DanError]

for _ in cs50p: print("I love it!!!")

[@edmund8954]

49:10 How does giving the sorted() function the key get_student(), which is comprised of just strings make sorted() know to sort by alphabetical order?

[@kvelez]

printed_names = set() with open("./names.csv") as file_csv: for line in file_csv: name, house = line.rstrip().split(",") student = {"name": name, "house": house} if name not in printed_names: print(name, house) printed_names.add(name)

[@miaomar3228]

Could the key in the sorted function at 53:06 instead of get_house be student[“name”] or student[“house”] ?

[@caiofernando]

Per the documentation key should be a function that returns the values to be sorted.

[@caiofernando]

@SlimyBlockhead key has to be a function. What sorted() does is it feeds each variable to the function and uses the returned values to sort.

[@k.o.o.p.a.]

holy information overload batman

[@marcosernestogarayracca2928]

excelent

[@DarkAcademyUniversity]

excellent :)

[@TanzidTushar]

if your code shows error like Module not found , you can do pip install pillow in your terminal and then it should work fine . in my vscode it didn't work by default so I had to install the package through command line .

[@ProgrammerPenguin]

the costume1.gif and costume2.gif doesn't work it shows an error "an error occurred while loading the image vs code"

[@BhavyamMittal-gi3jn]

I have another problem that is when I import Image from PIL(i type "from PIL import Image"), it says that the module doesn't exist because of which i can't even use image and the saving part

[@gregcruz6517]

when i do the code at 18:53 , it will print each list item as a list item. i find add [0] to the end for each name, as before.

[@kevinchou1280]

had to watch three times to understand this lol

[@samuelmiscik5667]

51:00 sorted(students, key=get_name, reverse=True) Does (students, key=get_name) just looks at every key (name) in dict and just makes a list out of them? Because i have no idea and i dont really get how it works....its because of the key=get_name? Shouldnt there be some kind of append or something? I am really confused can someone explain how it works? thanks

[@farhanishraq5812]

can you please make a series for java?

[@hajarbenabou7040]

I have a question: When I try to submit my work in the problem set, I can't submit my other file(the one that we will count its lines) Am I doing something wrong or it wont be submitted anyway ?

[@BT-te9vx]

firstly, thank you for the course & simplest explanations. Although I have "kind of" figured it by experimentation, I still am not very clear on the parameter naming in the lambda function. what I mean is, in the given example, could I use any name(parameter) after lambda(instead of "student") - i realised after multiple tries that I had to change all names (and it is demotivating to realise that I don't understand something very basic here). For eg. the original code was for student in sorted(students, key = lambda student: student["name"]): print(f"{student['name']} is from house {student['house']}") I wanted to check my understanding and change the parameter name in the lambda function to something else (like 'x') - and something like this doesn't work for student in sorted(students, key = lambda x: x["name"]): print(f"{x['name']} is from house {x['house']}") what ultimately works (and is obviously the right approach - BUT I JUST DON'T "GET IT") is : for x in sorted(characters, key = lambda x: x["name"]): print(f"{x['name']} is from house {x['house']}") will rattle my brain more on this - but if someone has some tip to make me understand this better, I'd be obliged. TIA and keep learning

[@lukimaster2]

for student in sorted(students, key = lambda x: x["name"]): print(f"{student['name']} is from house {student['house']}") Should work

[@joynil7211]

Hey, David. To begin with, I'd like to thank you for such an amazing course. It really has helped me a lot in my journey to learning python. So, I was trying to practice the PIL library function on my own using the cs50.dev . But I'm unable to upload or open the .gif images. It'd be great if you could just help me with it. Tell me how to import images on Virtual Studio code for cs50. Thanks

[@joynil7211]

Also, I believe I need to add extensions for that. If that's the case, can you suggest me some verified working good extensions? I'd be grateful.

[@JahKor-ht8rd]

pls about the csv reader, after running the codes mine repeated for four times and i dont know where my bugs coming from pls Need and a hand on this A S A P.

[@jacquessantiago]

When he wanted to change the data storage format "txt" tile into "csv", He created a new file. Is it possible to convert a txt file to csv file from our code?

[@Hellmiauz]

import os os.rename('names.txt', 'names.csv') you can o that. it's just changing the file extension. since both are "plain text" files there's nothing special about them, both are files that contain text, one happens to have commas.

[@Stella2U]

How do you do math operations on values? IEven with adding int(value) , it gives errors.

[@mj-pt2ty]

why does it say an error has occured when i try accessing the gif?

[@DuongThiMinhThu_]

when I trying to code the files costume1.gif and costume2.gif, I have a problem "an error occured while loading the image". Are there anyone who have the same problem with me, can you give me an instruction to fix this, thank you.

[@cheeseballs9579]

did you find a fix, i've been trying for an hour now

[@sakethreddyburugu1156]

@@cheeseballs9579 I've had the same problem but I resolved it by : 1. Download the image from the source code if you haven't. 2. If you've accidentally installed PIL instead of pillow, you'll have to delete PIL first and then download pillow. 3. And then I installed PIL from my command line and it somehow worked for me. 4. Sometimes installing library off the path could would lead to errors when we try to use the libraries, so do check for it.

[@ifeanyiojji]

For this part 1:31:23 right here if your file isnt working try creating a variable specifying the name of the gif files

[@pgaming183]

Can I use a file in both append and read mode by using two with methods

[@chrisfielding143]

I know this is not what you are looking for coz your question asks for a single file, but you can write a new file while reading from an existing file. Here is an example: with open('names3.txt','r') as f: names=f.readlines() for name in names: print(f'Hello, {name.capitalize()}',end='') with open('names4.txt','a') as file: file.write(f'Hello, {name}')

[@abdullashafi580]

you wrote the codes , I wrote the codes you ran the codes, I ran the codes your code works, but mine....

[@pstefanics]

In the students.csv file, did you put quotes around "Number Four, Privet Drive" ? :)

[@jagzey]

@@pstefanics that had me stuck, forgot that i had to have the speech marks for DictReader to interpret it correctly

[@sayori3939]

Oooo can I've heard pil comes with converting functions, so can we build a file converter with it? :3 maybe that will be my python's final project

[@Analyzing_eye]

where do i practice these problems

[@jashwanthbablu856]

Sir but I have one doubt, in real life scenario where we use these files I/O , please clarify this please sir

[@davidjmalan]

Whenever you'd like to read information from files, or save information to files!

[@italiaman]

for the gif thing, images must have the same dimensions

[@hand-eye4517]

58:03 if only real life worked like that with a few lines of code . "I'm gonna change this house into a home"

[@stuartlevybaseball3604]

I am having issues with the csv.DictReader. When I enter in the information exactly as it is on the screen, it is saying that "name" and "home" are not defined. Help

[@stuartlevybaseball3604]

Or it will say KeyError: 'home' and I have entered in the syntax the exact same as on the screen. Was there an update or something?

[@stuartlevybaseball3604]

Wait nevermind. I had a space on my csv

[@meynoush535]

I was trying to create gif file with three pictures, instead of two. Yet it didn't work. can someone please help me?

[@meynoush535]

I resolved the bug by just adding other images to the list of append_images. Such that append_images=[images[1], images[2],... images[n]] Hope somebody finds it useful.

[@alptug]

I am really struggling to find a clean way to delete one row from csv file for example i want to delete "name": "harry" really couldnt find a way

[@luanpires1784]

I've searched for how to delete a dictionary from a list in python. You can do it like this: import csv students = [] with open("students.csv") as file: reader = csv.DictReader(file) for row in reader: students.append(row) for i in range(len(students)): if students[i]["name"] == "Harry": del students[i] break for dictionary in students: print(dictionary)

[@alptug]

@@luanpires1784 thanks a lot for the reply i will check once i get back

[@osmansafi4517]

I am an Electrical Engineer want to learn python for my project for data alalysis, machine learning etc. is this the right place ? NEED your HELP.

[@sudipadhikari869]

How to download PIL library ??

[@relaxer7329]

Pip PIL install

[@pgaming183]

What happens if we open a file that does not exist with read mode

[@jagzey]

try it

[@qianwang8639]

looking forward lecture7&8

[@manalbutt1332]

Yes! Regular Expression and Object Oriented Programming are your next ones. You got this.

[@sayori3939]

Regex... I think... I may die in that one also OOP i never could understand any program using oop even if it had simple logic( I KNOW what class is, inheritance and all oop stuff) , that always made me mad i hope david can close that gap 😢😢😢

[@zakariyahussain1607]

@@sayori3939 bruv i seen u everywhere commenting on the CS50 stuff

[@sayori3939]

@@zakariyahussain1607 :3

[@zakariyahussain1607]

@@sayori3939 send me ur disc

[@yousefali755]

Still waiting 🖤

[@Chibudomobasi]

4 years later and he still dresses the same

[@roitv2463]

I'm waiting

[@kojo7485]

I'm learning 😌

[@thatsawesome.]

Jeez!

[@MisterK-YT]

Every time I see the puppets I lol.

[@gaganarora4656]

David Malan for President 2024

[@codelivewithme]

dot making extention in vs code ? ? i need )/

[@sayori3939]

I believe that's a setting not an extension I'm not sure, maybe search "indentation" in the settings

[@monicagalloriofrio9551]

this is really usefull.. David you tipe soooo fast..

[@codelivewithme]

dark mode will be more perfect fit

[@TheNuncFluens]

David always wears black not enough contrast

[@kylofps]

My brain hurts! (this is a good thing)

[@taimurkhan3881]

Waiting...

[@rukiyearcan2192]

great course, great professor really but enough about this harry potter

[@LAAL0_O]

can't wait for the exercise to be 20x harder than this lecture.

[@amine63404]

01:14:04

[@jb6164]

1:24:24 I am not able to load the image - returns An error occurred while loading the image. Anyone can help to fix it?

[@sulimansal2990]

in c or ...?

[@yousefali755]

Think in python

[@JamesRodriguez10783]

@@yousefali755 Python. Nooo, god. Please stop.

[@manalbutt1332]

This course is called CS50P, which means CS50, programming with python. You can find the course here: cs50.harvard.edu/python/2022/ And you can find the week 6 here: cs50.harvard.edu/python/2022/weeks/6/

[@Patriot513]

I'll call it "Jiff" when "Graphics" from Graphics Interchange Format (GIF) is pronounced Jraphics... :D

[@sushmasingh9040]

btw david sir looks like moriarty

[@pushpakumari1801]

1:05:34

[@DM-ul5yc]

"People are the problem" that's what a robot would say.

[@ednja]

David Malan must be an AI character because it's been 7 weeks and he hasn't changed his clothes since the 1st week.

[@lilninja937]

I refuse to call it a jif 😤

[@Xero-23]

Bruh why did youtube think that im interested in this video?

[@manalbutt1332]

Everyone should be. It is a well-taught course. I have taken it. And you should too.

[@Xero-23]

@@manalbutt1332 i know absolutly nothing about this course it was just randomly recommended to me

[@manalbutt1332]

I knew nothing too. You can start watching from week 0, up to this one. You will understand everyhing.

[@sayori3939]

Bc sometimes yt recommends quality stuff instead of click bait with inappropriate thumbnails :3 it's a sign, learn programming! Uuuuuuuuu

[@ken305]

35:00

[@huwrw007]

25:00

[@error079]

python is f'ed up. where is the data read? I see no more file.readlines()

[@sayori3939]

yummy :3