Loops

Loops#

Exercise 1: Fix the error#

weights = [1243891290, 1234129401, 14910395130, 1340981394]

# your solution here
for index in range(10):
    item = weights[index]
    print(item)

1243891290
1234129401
14910395130
1340981394

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Cell In[11], line 5
      3 # your solution here
      4 for index in range(10):
----> 5     item = weights[index]
      6     print(item)

IndexError: list index out of range

Exercise 2: Fix the error#

Below code only prints one list element. Which is it? Can you fix the code so that each list element is printed?

weights = [1243891290, 1234129401, 14910395130, 1340981394, 1231032912, 90000000]

# your solution here
for idx in range(len(weights)):
    item = weights[idx]
print(item)

1243891290
1234129401
14910395130
1340981394
1231032912
90000000

Exercise 3: Printing using a for loop#

Use a for loop to each list element in a separate line:

ages = [12, 43, 89, 64, 52]

# your solution here

Exercise 4: Convert units#

We have a list of weights in grams. Use a for loop to convert the weights to tons and print them one by one.

grams = [1243891290, 1234129401, 14910395130, 1340981394]

# your solution here

Exercise 5: Generating ranges with a specific content#

Create a range statement with

  1. 2 elements

  2. 10 elements

  3. These elements: [0, 1, 2, 3, 4, 5, 6]

  4. Elements starting at 3 and ending with (including 6): [3, 4, 5, 6]

  5. Every 3rd element, up to 10: [0, 3, 6, 9]

  6. All EVEN numbers (including zero) up to and including 8: [0, 2, 4, 6, 8]

  7. All ODD numbers up to 8: [1, 3, 5, 7]

Test your result by printing the contents of the range-object. You can do so by first casting it to a list, and then printing it.

# your solution here
r = range(1,8, 2)
print(list(r))

[1, 3, 5, 7]

Exercise 6: Ranges and loops#

The following code is supposed to generate a list that only contains the items at even indices (indices [0, 2, 4, …]) from the list all_values.

Does it produce the correct result? If not, fix it!

all_values = [34, 5, 11, 83, 432, 3, 50, 780]

even_values = []
for index in range(0, len(all_values), 2):
    item = all_values[index]
    even_values.append(item)

print(even_values)

[5, 83, 3, 780]

Exercise 7: Print every other element of the list, starting with the second#

Use a for loop and range.

weights = [567803, 1243891290, 1234129401, 14910395130, 1340981394, 1231032912, 90000000]

# your solution here:
# the code should print the following numbers [1243891290, 14910395130, 1231032912]
for index in range(1, len(weights), 2):
    print(weights[index])

1243891290
14910395130
1231032912

Bonus: Now achieve the same result, but use slice indexing instead:

# your solution here:
for weight in weights[1::2]:
    print(weight)

1243891290
14910395130
1231032912

Exercise 8: Convert units and append the results to a new list#

We have a list of weights in grams - create a new list, called tons that contains the weights in tons.

grams = [1243891290, 1234129401, 14910395130, 1340981394]

# your solution here

Exercise 9: Filtering a list (1)#

Print all list elements greater than 10:

a = [34,5, 432, 3, 780]

# your solution here
for idx in range(len(a)):
    if a[idx] > 10:
        print(a[idx])

34
432
780

Exercise 10: Filtering a list (2)#

Create a new list that contains all elements greater than 10:

a = [34, 5, 432, 3, 780]

# your solution here
greater = []

for num in a:
    if num > 10:
        greater.append(num)

print(greater)

[34, 432, 780]

Exercise 11: Filtering a list (3)#

Create a new list that contains all elements greater than 10 and less than 100:

a = [34, 5, 11, 83, 432, 3, 50, 780]

# your solution here
greater = []

for num in a:
    if num > 10 and num < 100:
        greater.append(num)

print(greater)

[34, 11, 83, 50]

Exercise 12: Slice indexing#

The following code is supposed to generate a list that only contains the items at even indices (indices [0, 2, 4, …]) from the list all_values.

Does it produce the correct result? If not, fix it!

all_values = [34, 5, 11, 83, 432, 3, 50, 780]

even_values = []
for index in range(0, len(all_values), 2):
    item = all_values[index]
    even_values.append(item)

print(even_values)

[34, 11, 432, 50]

Exercise 13: Updating a variable#

The following code is supposed to compute the sum of the values in the list all_values.

Does it produce the correct result? If not, fix it!

all_values = list(range(10))
print(all_values)

# fix this code:
sum_of_values = 0

for value in all_values:
    sum_of_values += value

sum_of_values

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

45

Exercise 14: Write a spike detector#

Now write a spike detector:

  1. Iterate over the voltage values in voltages using a for loop. You will need a range object.

  2. Compare each voltage value to the spike_threshold,

  3. Append the indices of voltage values that exceed spike_threshold to the list spike_indices

Before you start coding: What are the expected results? How many spikes does voltages contain? At which indices?

voltages = [1, 1, 10, 1, 1, 10, 1]
spike_threshold = 5

spike_indices = []

# your solution here
spike_indices = []

for idx in range(len(voltages)):
    BIG_V = voltages[idx]
    if BIG_V > spike_threshold:
        spike_indices.append(idx)
print(spike_indices)

[2, 5]
Contents