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Reference guide: Python concepts from module 1

This reference guide contains Python language introduced during module 1. The guide is organized into the following sections:

    Comments

    Functions

    Conditional statements

    Iterative statements

    Within each section, items generally appear in the order they were introduced.


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    Sections
    Comments
    Functions
    Conditional statements
    Iterative statements
    Comments
    The following syntax is used to create a comment. (A comment is a note programmers make about the intention behind their code.)
    #
    Starts a line that contains a Python comment

    # Print approved usernames
    Contains a comment that indicates the purpose of the code that follows it is to print approved usernames
     
    Functions
    The following functions are commonly used in Python. 
    print()
    Outputs a specified object to the screen

        print("login success")
    Outputs the string "login success" to the screen

    print(9 < 7)
    Outputs the Boolean value of False to the screen after evaluating whether the integer 9 is less than the integer 7
    type()
    Returns the data type of its input

        print(type(51.1))
    Returns the data type of float for the input of 51.1

    print(type(True))
    Returns the data type of Boolean for the input of True
    range()
    Generates a sequence of numbers

        range(0, 5, 1)
    Generates a sequence with a start point of 0, a stop point of 5, and an increment of 1; because the start point is inclusive but the stop point is exclusive, the generated sequence is 0, 1, 2, 3, and 4 

    range(5)
    Generates a sequence with a stop point of 5; when the start point is not specified, it is set at the default value of 0, and when the increment is not specified, it is set at the default value of 1; the generated sequence is 0, 1, 2, 3, and 4 

    Conditional statements
    The following keywords and operators are used in conditional statements. 
    if
    Starts a conditional statement

        if device_id != "la858zn":
    Starts a conditional statement that evaluates whether the device_id variable contains a value that is not equal to "la858zn"

    if user in approved_list:
    Starts a conditional statement that evaluates if the user variable contains a value that is also found in the approved_list variable
    elif
    Precedes a condition that is only evaluated when previous conditions evaluate to False; previous conditions include the condition in the if statement, and when applicable, conditions in other elif statements

        elif status == 500:
    When previous conditions evaluate to False, evaluates if the status variable contains a value that is equal to 500
    else
    Precedes a code section that only evaluates when all conditions that precede it within the conditional statement evaluate to False; this includes the condition in the if statement, and when applicable, conditions in elif statements 

        else:
    When previous conditions evaluate to False, Python evaluates this else statement

     
    and
    Requires both conditions on either side of the operator to evaluate to True

        if username == "bmoreno" and login_attempts < 5:
    Evaluates to True if the value in the username variable is equal to  "bmoreno" and the value in the login_attempts variable is less than 5
    or
    Requires only one of the conditions on either side of the operator to evaluate to True

        if status == 100 or status == 102:
    Evaluates to True if the value in the status variable is equal to 100 or the value in the  status variable is equal to 102
    not
    Negates a given condition so that it evaluates to False if the condition is True and to True if it is False

        if not account_status == "removed"
    Evaluates to False if the value in the account_status variable is equal to "removed" and evaluates to True if the value is the account_status variable is not equal to "removed"
    Iterative statements
    The following keywords are used in iterative statements. 
    for
    Signals the beginning of a for loop; used to iterate through a specified sequence

        for username in ["bmoreno", "tshah", "elarson"]:
    Signals the beginning of a for loop that iterates through the sequence of elements in the list ["bmoreno", "tshah", "elarson"] using the loop variable username

    for i in range(10):
    Signals the beginning of a for loop that iterates through a sequence of numbers created by range(10) using the loop variable i
    while
    Signals the beginning of a while loop; used to iterate based on a condition

        while login_attempts < 5:
    Signals the beginning of a while loop that will iterate as long as the condition that the value of login_attempts is less than 5 evaluates to True
    break
    Used to break out of a loop
    continue
    Used to skip a loop iteration and continue with the next one

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