Python - Basics

Reserved Words

Essential vocabulary in Python that cannot be used as Variables

Same

Single and double quotes do the () thing in Python

>>>

“What do you want me to do next?”

Interpreter

Python is an () language

Interpreter Language

Program that analyzes and executes each line of code.

Machine Language

Programming language using binary or hexadecimal instructions that a computer can directly respond to.

Variable

Item that holds a value while a program is running.

Compiler

Program that converts instructions into a machine-code so that they can be read and executed by a computer.

Symbol for quote(s)

‘ or “

String

A sequence of characters enclosed (like a sentence) in single or double quotes

Script

A file that holds Python instructions.

quit()

there is o need to have () at the end of the Python program in the file as it knows to stop when reaching the end.

Sequential execution

Perform statements one after another in the order they are encountered in the script.

Conditional execution

Check for certain conditions and then execute or skip a sequence of statements.

Repeated execution

Perform some set of statements repeatedly, usually with some variation.

Reuse

Give a set of instructions a name so you can use them again whenever you need to.

Syntax errors

An error when you violate the grammar rules of the program, such as forgetting () or quotes

Logic errors

When the program has proper syntax BUT there is a mistake in the order of statements or how they are related. “take a drink from your water bottle, put it in your backpack, walk to the library, and then put the top back on the bottle.”

Semantic errors

Statements are semantically correct AND in the right order, however does not intend what you want it to do (accidentally giving wrong directions)

Debugging

The process of finding the cause of the error in your code.

Random walk programming

Making random changes in the program until it works. Takes a while and can be inefficient.

Main memory

Where in the computer is a variable such as “x” stored after the following Python line executes?

Strings, quotation

() will be enclosed in () marks

Str

Symbol for String

Int

Symbol for Integer

Float (Floating Point)

For the purposes of this coding language, numbers with decimal points like 32.5 (approximate values)

String

The values “17” and “3.2” are what type (Note the quotations, what does that tell you?)

Commas, Quotations

To print an integer don't use () or ()

Bool

Symbol for Boolean

Boolean

A data type with two possible values: True or false

Variable

A name that refers to a value.

Number

Variables CANNOT start with a ()

Lower-case, upper-case

You should start variables with () letters as opposed to () case

Space

You cannot have a () in the variable name.

Statement

a unit of code that the Python interpreter can execute.

Assignment

The process of giving value to a variable is called a(n)

Operators

Special symbols that represent computations like addition and multiplication.

Exponentiation

What does ** mean?

//

To get an integer answer in python as opposed to a floating point in division, what symbol do you use?

%

Modulus operator

Expression, Interpreter

A combination of values, variables, and operators. ONLY WORKS IN AN ()

Concentration, +

Joining the strings by linking them end to end. What is the symbol used?

Multiply

You can also () strings by using *

Addition assignment operator (+=)

adds two values and assigns the sum to a variable (left operand). Ex:
X = 5
print("Value Before Change: ", X)
X += 15
print("Value After Change: ", X)

int()

What function is used to convert string values to integers?

\n

What sequence is used to create a newline at the end of statements?

Parse Error

Most common error in Python. Tends to occur when missing parenthesis or other syntax. Make sure parenthesis are balanced so the code runs correctly.

Type Error, integer

A coding error where you combine two objects that are not compatible, such as adding an () and string together.

Store, x = int(x)

int(x) converts the string to an integer, but doesn’t () it anywhere. In this case you may need to use the assignment statement (), as it changes what x references the RETURNED integer value (allowing us to avoid a type error such as adding an integer + string together)

NameError

A common type of error that comes from using a variable before it has a value or simply caused by typos in the code. You can tell if the word only appears once in the code on the right side of the assignment statement.

Variables

You need to keep track of the restrictions needed for your (), and understand what your function is expecting. You can do this by writing comments in your code, or by naming your variables in a way that reminds you of their proper form.

Backwards

Work () from the error. This is because what caused the error usually happens in the code before it.

Automatically

Using commas () inserts spaces

Strings

True and False are not (). There are bool

X is NOT equal to Y

x != y

==

Boolean 56

and, or, not

The three logical operators include (), () and ()

Not

The () operator negates a boolean

Condition

The boolean expression after the if statement is called the ()

Alternative execution

A second form of an if statement where there are two possibilities and the condition determines which one gets executed. Also known as branches

Elseif

There is no limit on the number of () statements. If there is an else clause, it has to be at the end, but there doesn’t have to be one.

Chained Conditionals

a "chain" or a combination or multiple conditions

Nested Statements

Simply putting code inside of other code. For example placing an if statement inside of an already existing if statement. Best to avoid or it becomes too messy.

Try, Except

() and () feature in Python as an “insurance policy” on a sequence of statements.

catching an exception

Handling an exception with a try statement

Left, Right

When Python is processing a logical expression such as x >= 2 and (x/y) > 2, it evaluates the expression from () to ()

Short-circuit evaluation

When the evaluation of a logical expression stops because the overall value is already known (I.E. evaluates the whole statement to be false)

Guard

In the second expression, we say that y != 0 acts as a () to insure that we only execute (x/y) if y is non-zero. This evaluation is to prevent a run-time error where it divides the equation by 0.

Green, Red, True, True, 0

() = True Statement (evaluates the whole expression as true and computes

() = False Statement (evaluates whole expression as false so it stops after the initial statement due to short-circuit evaluation)

The third statement produces a run-time error because since the first statement (x) is (), it also assumes the second statement is (). However, since Y is = to (), it attempts to divide it by that value.

Caused

In general, error messages tell you where the problem was discovered, but that is often not where it was ().

ValueError

Raised when an operation or function receives an argument that has the right type but an inappropriate value, and the situation is not described by a more precise exception such as IndexError. (A built in exception)

Function

named sequence of statements that performs a computation

Argument

a value or variable that we are passing into the function as input to the function. Inside the parenthesis of it.

Return

The result of the argument in a function

Built

The max and min functions that give us the highest/lowest values of each number is () into Python

Len (length)

tells us how many items are in its argument. Spaces ALSO count.

int(), float(), str(), NOT

Type conversion function examples. The int function does () round up

Math Module

provides most of the familiar mathematical functions.

Dot Notation

To access one of the functions, you have to specify the name of the module and the name of the function, separated by a dot. This is known as () () i.e. math.log10(ratio)

Random Module

provides functions that generate pseudorandom numbers

Choice

To choose an element from a sequence at random

Def

indicates that something is a function definition

Header, Body, Header, 4

The first line of the function definition is called the (), while the rest is called the (). The () must end with a : (colon). You should Indent () spaces after the header.

Error

If we move the function call above the definition we will get an ()