Strings and Escape Characters

• Anything within quotes is a string.
• The computer interprets strings differently from numbers.
• Using quotes indicates to the computer that something should be treated as words rather than numbers.
• Without quotes, the computer assumes the content is numeric.
• There is a difference between "4+3" (string) and 4+3 (numbers).

Escape Characters

• Escape characters serve special functions within strings.
• \" represents a double quote.
• \' represents a single quote.
• \\ represents a backslash.
• \n represents a new line.
• \t represents a tab.
• \b represents a backspace.
• print("Our logo "GO BEARS GO" ") will result in an error because of unescaped double quotes within the string.
• print("Our logo \"GO BEARS GO\" ") will output: Our logo "GO BEARS GO".

Type Casting

• int() converts the value within the parentheses to an integer, rounding down if necessary.
• float() converts the value within the parentheses to a floating-point number, adding .0 if necessary.
• str() converts the value within the parentheses to a string.
• int(3/2) results in 1.
• float(3) results in 3.0.
• str(5) results in "5".
• int("7") results in 7.
• int("abc") will result in an error because "abc" is not a valid integer.
• print("sum is" + 15) will result in an error because you cannot directly concatenate a string with an integer.
• print("sum is" + str(15)) will not have errors, because the integer has been converted to a string.
• print("3"*5) results in "33333".
• print(int("3") * 5) results in 15.

Using Strings

• Both single quotes (') and double quotes (") can define strings.
• Double quotes are best when the string contains a single quote.
• Single quotes are best when the string contains a double quote.

Variables

• Variables are named memory locations for storing data of a specific type.
• Known variable types so far include:
  • int (integers)
  • str (string)
  • float (real numbers)
• Python declares variables "on the fly."
• Variables should be declared at the top of the program for clarity.
• Example:
  • age = int()
  • name = str()

Rules for Variables

• Variable names cannot contain spaces.
• The first character of a variable name cannot be a digit; it must be a letter (a-z or A-Z) or an underscore (_).
• Remaining characters can include letters, digits, and underscores.
• Special symbols are not allowed in variable names, except for the underscore.
• Uppercase and lowercase characters are distinct (case-sensitive).
• Reserved words in python cannot be used as variables.
• Descriptive variable names are recommended.

Variable Types

• Integer (int) stores integer numbers.
• String (str) stores letters and words.
• Floating point (float) stores decimals.
• Boolean stores (True or False) values.

What Var Type it Should Be:

• Your age: int
• Your name: str
• Pi: float
• The distance between Toronto and Montreal: float or int (depending on desired precision)
• Today's Date: str or a custom date object
• The number of apples in a bushel: int

Math Operators

• // divides two numbers and discards the remainder (integer division).

• ** indicates exponents (e.g., 2**3 is 2 to the power of 3).

• % gives the remainder after division (modulus). For example, 7 % 3 = 1.

• 7 // 3 = 2.

• Division by zero is not allowed.

• math.sqrt() will return the square root of a number.

• math.pi represents the mathematical constant π (approximately 3.141592...).

• math.ceil(x) returns the ceiling of x, which is the smallest integer greater than or equal to x. For example, math.ceil(3.5) returns 4, and math.ceil(-5.3) returns -5.

• math.fabs(x) returns the absolute value of x.

• math.factorial(x) returns x factorial. Raises ValueError if x is not integral or is negative.

• Examples: math.factorial(3) returns 6. math.factorial(4) returns 24.

• math.floor(x) returns the floor of x, the largest integer less than or equal to x. For example, math.floor(3.5) returns 3, and math.floor(-5.3) returns -6.

• math.pow(x, y) returns x raised to the power y. For example, math.pow(2,3) returns 8.

• math.cos(x) returns the cosine of x radians.

• math.hypot(x, y) returns the Euclidean norm, which is the length of the vector from the origin to point (x, y). It is calculated as sqrt(x*x + y*y).

• math.sin(x) returns the sine of x radians.

• math.tan(x) returns the tangent of x radians.

• math.degrees(x) converts angle x from radians to degrees.

• math.radians(x) converts angle x from degrees to radians.

Explore strings and escape characters. Learn how computers interpret strings differently from numbers. Understand the use of escape characters such as ", \, \n, and type casting with int() and float().