Controlling loop execution

A typical pattern is to create a while loop with True as its condition and use a break statement to end it. In this exercise, your manager wants you to assemble a list of the five most recent years that the US had a positive trade gap. The dictionary nea is a mapping of datetimes to floats representing the net export for a given year. An empty list named surplus_years and a datetime named query_date are supplied.

This exercise is part of the course

Intermediate Python for Finance

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Exercise instructions

Create a loop with a condition that is always true.
Skip steps where net exports are less than zero.
Check the number of surplus years gathered.
Stop the loop once five years have been gathered.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# Loop while true
while ____:
    net_exports = nea.get(query_date, -1)
    query_date = datetime(query_date.year - 1, 1, 1)
    # Skip if net exports are not positive
    if net_exports < 0:
        ----   
    surplus_years.append(query_date)
    # Check if 5 years have been collected
    ____ len(surplus_years) == 5:
        # Stop the loop
        ----
print(surplus_years)

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