The os Library , List a file, Create a folder, Renames a file

The os Library

Today's lesson is going to use the os library to create folders and navigate around them.

Previously, we've used os to clear the screen.

Here are a few other things that it can do:

List a file

👉 listdir() will allow you to list all the files:

import os

print(os.listdir()) # Lists all the files in the current directory. Useful for checking that a file is in the folder we think it is.

files = os.listdir()

if "quickSave.txt" not in files:

print("Error: Quick Save not found.")

#Checks if a file is in a directory and outputs an error if not.

Create a folder
👉 Try this code with os.mkdir():

import os

os.mkdir("Hello") # Creates a folder called 'Hello'

Renames a file

👉 os.rename() takes 2 arguments: the file to rename and the new name.

import os
os.rename("myname.txt", "NEW.o")

Comments

FOR LOOP , RANGE

FOR LOOP A while loop is perfect to use when we don't know how many times we want the loop to repeat. If we have an idea of how many times we want the loop to repeat, we can use a for loop to loop code in exactly the same way the while loop did. EXAMPLE : for counter in range(10): print(counter) RANGE The range function creates a list of numbers in the range you create. If you only give it one number, it will start at 0 and move to a state where the final number is one less than the number in the brackets. In this case, the final number would be 9 . EXAMPLE : total = 0 for number in range(100) : total += number print(total)

CONTINUE COMMAND AND EXIT LINE

The Continue Command The continue command stops executing code in the loop and starts at the top of the loop again. Essentially, we want to kick the user back to the original question. EXAMPLE : while True: print("You are in a corridor, do you go left or right?") direction = input("> ") if direction == "left": print("You have fallen to your death") break elif direction == "right": continue else: print("Ahh! You're a genius, you've won") NOTE : The else statement refers to any input besides left or right (up or esc). Since the user is a winner, we do not want to use break or it would say they have failed. EXIT COMMAND LINE The previous code continues to loop even after the user has won. Let's fix that with the exit() command EXAMPLE: print("Let's play chutes and ladders. Pick ladder or chute.") while...

IF AND ELSE STATEMENT

If Statements These statements are a bit like asking a question. You are telling the computer: if something is true, then do this specific block of code. Double equals ( == ) is asking the computer to compare if these two things are exactly the same. EXAMPLE : myName = input("What's your name?: ") if myName == "David": What is else? IF the condition is not met with the if statement, then we want the computer to do the else part instead. Likewise, if the condition is met in the if statement, then the else bit is ignored by the computer. The else statement must be the first thing unindented after the if statement and in line with it EXAMPLE : myName = input("What's your name?: ") if myName == "David": print("Welcome Dude!") print("You're just the baldest dude I've ever seen...

PYTHON SYNTAX

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