Python is a general-purpose programming language and has overtaken Java in popularity according to a recent Stackoverflow survey.
People who have never programmed before are tempted to try due to the simplicity to learn and use it. Well, let's get down to business.
Before we get started
Before we get started, there are a few things you should know about python:
- Python is a high-level programming language, which means it has a strong abstraction from the computer's details (that's why it's so easy and understandable). Because of that, it may be not so efficient as other languages like assembly, C, or C++;
- Python is an interpreted language. Its syntax is read and then executed directly. The interpreter reads each program statement, following the program flow, then decides what to do and does it. That's why you should test all your programs, even if everything seems to be working correctly. If there is an error within a loop, for example, it will only be shown if the loop is executed;
- Python has excellent documentation that you can access here and an incredible community. Use them.
We are assuming that you have already installed python. If you do not, please click here.
To write your first Python code, open your text editor and type:
print("Hello world, this is my first python code")
Save the file as
helloworld.py and put it into the python interpreter to be executed.
You also can run your code on the command line:
C:\Users\Your Name>python helloworld.py
If everything went well, you should see something like this:
> Hello world, this is my first python code
You can also use the print function to show integers, variables, lists, etc. Try it!
#show the sum of two integers number1 = 5 number2 = 7 print(number1+number2)
#dividing two decimals number1 = float(12.1) number2 = float(4)
#concatenating strings name = "Python" phrase = str("I hate ") print("I love ", name) print(phrase+name)
Python has the following data types built-in by default, in these categories:
- Text Type:
- Numeric Types:
- Sequence Types:
- Mapping Type:
- Set Types:
- Boolean Type:
- Binary Types:
Note: Variables in Python are interpreted as integers by default. Is a good practice to declare them as another type explicitly (if they aren't integers). You can see the kind of a variable using the function
Operators are used to performing operations on variables and values. The main groups are:
- Arithmetic operators
- Comparison operators
- Logical operators
Arithmetic operators are used with numeric values to perform common mathematical operations.
x + y
x - y
x * y
x / y
x % y
x ** y
- Floor division:
x // y
Comparison operators are used to compare two values.
x == y
- Not equal:
x != y
- Greater than:
x > y
- Less than:
x < y
- Greater than or equal to:
x >= y
- Less than or equal to:
x <= y
Logical operators are used to combine conditional statements.
- and -> Returns True if both statements are true
x < 2 and x < 4
- or -> Returns True if one of the statements is true
x < 10 or x < 9
- not -> Reverse the result, returns False if the result is true
not(x < 2 and x < 4)
Look to the code below:
age = 18 if (age<21): print("The student is underage!") elif (age==21): print("The student is 21!") else: print("The student isn't underage!")
In programming, we often have to choose what to do depending on the situation. It is essential to know how to use conditional arguments like
The code above print a different message according to a condition.
Try to write a code that asks for two test scores. If the average is less than 7, the user should see "I'm sorry, you didn't do well on the tests". If the average is exactly 7, the user should see "You did it!". And if it is greater than 7, the user should see "Congratulations!! You're a great student.".
Note: to request a response from the user, you need to use the
input()function. For example:
name = str(input("What's your name?")) age = int(input("How old are you? ")) print("I'm %s and I'm %d"% (name, age))
Python has two primitive loop commands:
With the while loop, we can execute a set of statements as long as a condition is true.
count = 0 while count < 10: print(count) count += 1 #this line is the same as count = count+1
The code above will print count as long as count is less than 10.
A for loop is used for iterating over a sequence. Using it, we can execute a set of statements, once for each item in a list, tuple, set, string, etc. For example:
#loop through a string for x in "banana": print(x)
#loop through a list of fruits fruits = ["apple", "banana", "melon"] for x in fruits: print("I like", x)
Did you understand why python became so popular? In a few minutes, you were able to learn the main concepts of this fantastic language.
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