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COMP 1000: Think Like a Computer: The PreTeXt Interactive Edition

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Section 4.12 πŸ‘©β€πŸ’» Keeping Track of Your Iterator Variable and Your Iterable

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When students first begin using for loops, they sometimes have difficulty understanding the difference between the iterator variable (the loop variable) and the iterable.
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The iterable is the object that you will be parsing through in a for loop, typically a String, list, or other type of sequence. Generally, this object does not change while the for loop is being executed.
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The iterator (loop) variable is the variable which stores an element of the iterable (such as an item in the list or a single character from a String) when the for loop is being executed. Each time the loop iterates, the value of the iterator variable will change to a different element of the iterable.
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Checkpoint 4.12.1.

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    What is the type of your iterable?
    n = ["word", "phrase", 8, "beam"]
for item in n:
    print(item)
  • string
  • Incorrect, that is not the type of the iterable.
  • list
  • Yes, the iterable is n, and it is a list.
  • iterable
  • Incorrect, that is not the type of the iterable.
  • error, unable to iterate over the object.
  • Incorrect, Python can iterate over this type.
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Checkpoint 4.12.2.

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    What is the type of your iterable?
    t = "couch"
for z in t:
    print(z)
  • string
  • Yes, the iterable in this example is a string
  • list
  • Incorrect, that is not the type of the iterable.
  • iterable
  • Incorrect, that is not the type of the iterable.
  • error, unable to iterate over the object.
  • Incorrect, Python can iterate over this type.
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Checkpoint 4.12.3.

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    What is the type of your iterable?
    y = 18
for z in y:
    print(z)
  • string
  • Incorrect, there are no strings present in the code.
  • list
  • Incorrect, there are no lists present in the code.
  • iterable
  • Incorrect, there are no iterable objects in the code.
  • error, unable to iterate over the object.
  • Yes, Python is unable to iterate over integers and floats.
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Checkpoint 4.12.4.

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    What is the type of your iterable?
    t = ["couch", "chair", "washer", "dryer", "table"]
for z in t:
    print(z)
  • string
  • Incorrect, the iterable is not a string.
  • list
  • Yes, the iterable is t, and it is a list.
  • iterable
  • Incorrect, that is not the best answer for this problem.
  • error, unable to iterate over the object.
  • Incorrect, Python can iterate over this type.
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Checkpoint 4.12.5.

    πŸ”—
    What is the type of your iterable?
    t = "couch"
for z in t:
    print(z)
  • string
  • Correct! The iterable is a string.
  • list
  • Incorrect, there is no list in the code.
  • iterable
  • Incorrect, that is not the best answer for this problem.
  • error, unable to iterate over the object.
  • Incorrect, Python can iterate over this type.
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Checkpoint 4.12.6.

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    What’s the type of your iterator variable?
    t = ["couch", "chair", "washer", "dryer", "table"]
for z in t:
    print(z)
  • string
  • Correct! Every item in the iterator variable will be a string.
  • list
  • Incorrect, that is not the type of the iterator variable.
  • integer
  • Incorrect, that is not the type of the iterator variable.
  • error, unable to iterate and initialize the iterator variable
  • Incorrect, the for loop is iterating over an iterable object.
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Checkpoint 4.12.7.

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    What’s the type of your iterator variable in the first iteration?
    t = [9, "setter", 3, "wing spiker", 10, "middle blocker"]
for z in t:
    print(z)
  • string
  • Incorrect, think about what the for loop will look at first.
  • list
  • Incorrect, that is the type of the iterable, not the iterator variable.
  • integer
  • Yes, the first item in t is an integer.
  • error, unable to iterate and initialize the iterator variable
  • Incorrect, the for loop is iterating over an iterable object.
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Checkpoint 4.12.8.

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    What’s the type of your iterator variable in the second iteration?
    t = [9, "setter", 3, "wing spiker", 10, "middle blocker"]
for z in t:
    print(z)
  • string
  • Yes, the second item in t is a string.
  • list
  • Incorrect, that is the type of the iterable, not the iterator variable.
  • integer
  • Incorrect, think about what the for loop will look at during the second iteration.
  • error, unable to iterate and initialize the iterator variable
  • Incorrect, the for loop is iterating over an iterable object.
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Checkpoint 4.12.9.

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    What’s the type of your iterator variable in the final iteration?
    red = "colors"
for blue in red:
    print(blue)
  • string
  • Yes, the last value stored in the iterator variable is a string.
  • list
  • Incorrect, there is no list in the code.
  • integer
  • Incorrect, there is no integer in the code.
  • error, unable to iterate and initialize the iterator variable
  • Incorrect, the for loop is iterating over an iterable object.
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