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We now present a couple of code examples to illustrate the use of the elements just discussed. Figure 2.1 illustrates some Python code statements in a file (Fig 2_1 Python code example 1.py).

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Figure 2.1 Python Code Example 1

Several details in the Python code in Figure 2.1 are fundamental to writing programs in Python. Lines 1, 3, and 5 have comments that take up an entire line, and line 4 shows an example of a comment that makes a note at the end of a line of code. Line 4 is an assignment statement in which the right-hand side is a value in quotes. The value within quotation marks is a string-type value. When the code in line 4 executes, the trip_id variable will be a string. Line 5 illustrates the use of two built-in functions to report the data type of the just created trip_id variable. Specifically, a type function is within a print function. We already used the Python built-in print function in the example presented in Chapter 1. The type function in Python determines the data type of an object. Line 8 of the Python code in Figure 2.1 is an assignment statement in which the right-hand side is a number. When the code in line 8 executes, the trip_seconds variable will be an integer. The type function is also in line 9, which reports the data type for the just constructed trip_seconds variable. The output of these code statements is in Figure 2.2.

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Figure 2.2 Output from Execution of Python Code in Figure 2.1

Examining the output shown in Figure 2.2, we see that the data type for the trip_id variable is a string and the data type for the trip_seconds variable is an integer. The output messages specifically indicate that trip_id is of class “str” and that trip_seconds is of class “int.”

Our next example is like the first example but illustrates the construction of float and Boolean variables. Line 2 in Figure 2.3 assigns the value 1.1 to the variable trip_miles and line 3 prints out the data type of the trip_miles variable. Line 6 assigns the value True to the variable trip_completed. Note that True is a Python keyword shown in Table 2.1 and is in blue font in Figure 2.3. Also note that there are not parentheses around True, because if there were, it would be a string instead of the logical value True. Line 7 then prints out the data type of the trip_completed variable.

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Figure 2.3 Python Code Example 2

Examining the output shown in Figure 2.4, we see that the data type for the trip_miles variable is in fact a float and the data type for the trip_miles variable is a Boolean.

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Figure 2.4 Output from Executing Code Example 2