Learn to Program 8
Welcome to part 8 of my Learn to Program series. This time we’ll cover how to read and write files. I’ll answer a question I received about recursive functions. We’ll investigate what a Tuple is. And, of course we’ll work our way through problems so we can get better at solving programming problems.
All of the code follows the video below. It is heavily commented and is meant to be used to aid in the learning process.
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Code And Transcript
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# ---------- READING & WRITING TEXT ---------- # The os module provides methods for file processing import os # We are able to store data for later use in files # You can create or use an already created file with open # If you use w (write) for mode then the file is # overwritten. # If you use a (append) you add to the end of the file # Text is stored using unicode where numbers represent # all possible characters # We start the code with with which guarantees the file # will be closed if the program crashes with open("mydata.txt", mode="w", encoding="utf-8") as myFile: # You can write to the file with write # It doesn't add a newline myFile.write("Some random text\nMore random text\nAnd some more") # Open the file for reading # You don't have to provide a mode because it is # read by default with open("mydata.txt", encoding="utf-8") as myFile: # We can read data in a few ways # 1. read() reads everything into 1 string # 2. readline() reads everything including the first newline # 3. readlines() returns a list of every line which includes # each newline # Use read() to get everything at once print(myFile.read()) # Find out if the file is closed print(myFile.closed) # Get the file name print(myFile.name) # Get the access mode of the file print(myFile.mode) # Rename our file os.rename("mydata.txt", "mydata2.txt") # Delete a file # os.remove("mydata.dat") # Create a directory # os.mkdir("mydir") # Change directories # os.chdir("mydir") # Display current directory print("Current Directory :", os.getcwd()) # Remove a directory, but 1st move back 1 directory # os.chdir("..") # os.rmdir("mydir") # ---------- PROBLEM : Fibonacci sequence ---------- # Previously we generated 1 number in the # Fibonacci sequence. This time ask the user to define # how many numbers they want and display them # The formula for calculating the Fibonacci sequence is # Fn = Fn-1 + Fn-2 # Where F0 = 0 and F1 = 1 # Sample Output ''' How many Fibonacci values should be found : 30 1 1 2 3 5 All Done ''' def fib(num): if num == 0: return 0 elif num == 1: return 1 else: result = fib(num - 1) + fib(num - 2) return result numFibValues = int(input("How many Fibonacci values should be found : ")) i = 1 # While i is less then the number of values requested # continue to find more while i < numFibValues: # Call the fib() fibValue = fib(i) print(fibValue) i += 1 print("All Done") # ---------- READ ONE LINE AT A TIME ---------- # You can read 1 line at a time with readline() # Open the file with open("mydata2.txt", encoding="utf-8") as myFile: lineNum = 1 # We'll use a while loop that loops until the data # read is empty while True: line = myFile.readline() # line is empty so exit if not line: break print("Line", lineNum, " :", line, end="") lineNum += 1 # ---------- PROBLEM : ANALYZE THE FILE ---------- # As you cycle through each line output the number of # words and average word length ''' Line 1 Number of Words : 3 Avg Word Length : 4.7 Line 2 Number of Words : 3 Avg Word Length : 4.7 ''' with open("mydata2.txt", encoding="utf-8") as myFile: lineNum = 1 while True: line = myFile.readline() # line is empty so exit if not line: break print("Line", lineNum) # Put the words in a list using the space as # the boundary between words wordList = line.split() # Get the number of words with len() print("Number of Words :", len(wordList)) # Incremented for each character charCount = 0 for word in wordList: for char in word: charCount += 1 # Divide to find the answer avgNumChars = charCount/len(wordList) # Use format to limit to 2 decimals print("Avg Word Length : {:.2}".format(avgNumChars)) lineNum += 1 # ---------- TUPLES ---------- # A Tuple is like a list, but their values can't be changed # Tuples are surrounded with parentheses instead of # square brackets myTuple = (1, 2, 3, 5, 8) # Get a value with an index print("1st Value :", myTuple[0]) # Get a slice from the 1st index up to but not including # the 3rd print(myTuple[0:3]) # Get the number of items in a Tuple print("Tuple Length :", len(myTuple)) # Join or concatenate tuples moreFibs = myTuple + (13, 21, 34) # Check if a value is in a Tuple print("34 in Tuple :", 34 in moreFibs) # Iterate through a tuple for i in moreFibs: print(i) # Convert a List into a Tuple aList = [55, 89, 144] aTuple = tuple(aList) # Convert a Tuple into a List aList = list(aTuple) # Get max and minimum value print("Min :", min(aTuple)) print("Max :", max(aTuple)) |
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