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Python example 'lesson1-WhileLoops'
lesson1-WhileLoops
Python beginners example: lesson1-WhileLoops
# Just give the user some basic instructions. For the rest of this unit,
# simple lines like this will not be commented as thoroughly.
print("I'll ask you for a bunch of text. Type \"done\" when you are finished.")
# Create an empty string. Although the string is empty right now, we will add
# to it as we go through the program.
combinedText = ""
# Another string that will eventually represent the user's input to the
# program. Although this string does have some content (and I really do love
# platypi) the content is never shown to the user. We only need this string to
# not be empty so that we enter the loop on line 16.
userInput = "I like platypi."
# Here we use our first while loop. While is kind of like if because it tests
# the boolean expression, and enters the body of the loop if the expression is
# True. Unlike if, the while loop will continue to run over and over until the
# boolean condition becomes False.
while userInput != "done":
# Take some actual user input. Notice that this overwrites the previous
# contents of the userInput variable.
userInput = input("Enter some text then press enter. ")
# We'll add the input that the user just provided to the combinedText
# variable. Remember the + operator can be ussed to concatenate strings as
# as for actual math addition.
combinedText = combinedText + userInput
# Now the loop has ended. You can tell because these lines are un-indented.
# Since we are done taking input, we'll print(the output to the screen)
print(combinedText)
# ---------------- Exercises -----------------
# 1. Change the initial value of the string on line 14.
# Predict what will be different on the lines below. (Don't forget to comment
# them so they don't affect your program.)
# 2. Change the initial value of the string on line 8.
# Predict what will be different on the lines below. (Don't forget to comment
# them so they don't affect your program.)
# 3. The program currently uses the phrase "done" to indicate that the user is
# finished entering text. But if the user actually wants to enter the word
# "done" there is no way to do it. Modify line 20 so that entering a blank
# line will end the loop instead of the word "done".
# 4. Change line 29 to:
# combinedText += userInput
# This += operator is a shorthand for the full expression that we previously
# used. The shorthand can also be used in math. In fact, +=, -=, /=, *= are
# all valid math operators.
Useful links
- Learn Python: https://pythonbasics.org
- Download Python: https://python.org