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Python is the first language you should learn, but obviously not the only one.
A variable is a container in which you can store any data. For example, you can have the following variable:
With almost any programming language, you can create as many variables as you want or need. To start, in Python, you must declare the name of that variable with a unique name (relative to the value or what it receives)
The variable name is the most effective way to describe the content of a variable, use it wisely. It is important to choose a name that clearly indicates to you and other programmers what data is being stored in the variable. If you choose a bad or ambiguous name, your code will be almost impossible to understand, making it unusable. For example, let's change the name of our variable "age" to "a":
As you can see, the new variable name doesn't tell us anything about the data being stored and why it's being used.
Choosing the name of your variable is very important, so please don't use generic names. Be descriptive! A vague name will make it difficult to understand the purpose of the variable, especially for other programmers (including yourself).
As developers, we can set the value of a variable using the
= operator. You don't have to set the value of a variable when you declare it for the first time. You can set or reset (overwrite) the value as many times as you want and whenever you want. The value is always the last one you set. Here are some examples of how to set values to variables:
The values of variables can change over time. To retrieve the value of a variable, you can print its value on the screen at any time. Every programming language has its own methods for printing. In Python, we use
Variables can have different types of values:
|Booleano||True | False||Booleans are intended for logical operations. If you ask a computer something like, "Is X equal to 3?" it will respond with a boolean (true or false).|
|String||Any string of characters||Strings are the only way we have to store words (sequences of characters). Note: strings must be enclosed in quotes.|
|Number||Numbers only||Integers, negative numbers, decimals, floats, etc. All possible types of numbers. |
|Undefined||Empty||When a variable has no assigned value, it remains undefined.|
|Array||A list with any type of value.||A sequence of any type of values. They can be mixed types of values; for example: [2, 3, 'Word', 2, 1, null, 232, 5, 3, 23, 234, 5, 'hello'].|
|Objects||Any object||You can create your own data types with more complex operations. We will talk more about this later.|
|Null||Only Null||Used to specify when the database or any other function does not return anything.|
What operations can I perform with variables? Depending on the data type, you have some different possibilities:
Functions are pieces of code that can be reused multiple times during runtime, regardless of their position in the code. There are hundreds of reasons to use functions, but here are the top 2:
To declare a function in Python, you start with the
def keyword followed by the name you want to give to that function.
Then you specify the parameters (inputs) that the function will accept within parentheses.
Next, you start a new indented block of code where you write the code that your function should perform. Once you're done with the function's code, you simply stop the indentation.
Note: To return a value from the function, you use the
return keyword followed by the value you want to
return. You can place the return statement anywhere within the function's code block, and the function will exit and return that value.
Here is an example:
The scope of a variable determines where that variable is available for use. There are two main types of scopes:
A local variable is only available within the scope of the nearest curly braces. For example, variables passed as parameters to functions are only available within the content of that specific function.
If you declare a variable at the beginning of your code, it will be available throughout the entire code, even within the content of any particular function.
Computers think in black or white. Everything is true or false. All decisions on a computer boil down to a simple boolean. You can prepare a computer to solve particular problems by writing code that asks the right questions to solve that problem.
For example, if I want a computer to give candy only to children older than 13 years old, I can tell the computer to ask.
Is this child's age greater than 13 years? Yes or no?
In python, you can ask the computer to do the following logical operations:
|Equal to||==||Is 5 == 5? True!|
Is 5 == 4? False!
Is 5 == '5'? True!
|No Igual a||!=||Is 5 != 5? False!|
Is 5 != '5'? False!
Is 1 != 'Hello'? True!
|Greater than||>||Is 5 > 5? False!|
Is 6 > 3? True!
|Less than||<||Is 6 < 12? True|
|Greater or Equal||>=||Is 6 <= 6? True|
Is 3 <= 6? True
|Less or Equal||<=||You get the idea 🙂|
To create really useful operations, you can combine multiple operations in the same question using AND, OR, and NOT (and, or, or not respectively).
You can group logical operations within parentheses and use nested parentheses to perform multiple operations at the same time.
|AND||With AND, both sides MUST BE TRUE for everything to become true.|
Is (5 == 5 and 3 > 1) true? True!
Is ('Ramon' == 'Pedro' and 2 == 2) false? False
|OR||Is ('Oscar' != 'Maria' or 2 != 2) true? True!|
Is (5 == '5' and 'Ramon' != 'Pedro') or (2 == 2) true? True!
|NOT||NOT will be exactly the opposite of the logical operator's result:|
Is not (5 > 5) true? True!
Is not (True) false? False!
Now is when things start to get fun! To control your application's flow, you have several options, and you'll use them every day. So, you should feel comfortable using them.
The first tool you have is the
if...else conditional. It's straightforward. You can tell the computer to skip any part of your code depending on the current value of your variables.
if statement allows you to execute a block of code if certain conditions (or truths) are met. The "else" statement will execute an alternative block of code if the condition is false.
Python does not have the ability to use
It is possible to loop a segment of your code as many times as you want or need. Loops are one of the most important tools for developers these days.
Imagine you're in an elevator: the elevator must loop through the floors until it reaches the specific floor you want.
while loop will execute a block of code as long as a condition is true. Once the condition is false, the loop will stop executing the code.
For is similar to
while, with the only difference being that you must specify the condition to stop from the start. For that reason,
for is a bit more organized and easier to understand.
Note: when creating a loop, make sure the condition eventually becomes false to avoid an infinite loop. In an infinite loop, the code runs indefinitely and will freeze your browser.
For...in loops can be used to iterate over the properties of an object. Inside the parentheses, you can set any name to represent the information within the object and then include the name of the object:
Programming is like Taco Bell: the same ingredients are always used, but they are mixed in different ways. You know how to write code, but... do you know how to solve real-world problems?