DEV Community: Brayan Potosi

Loops in Python

Brayan Potosi — Sat, 09 Jan 2021 05:25:09 +0000

Loops are very used in programing when is necesary repeat a instruction x times. Some examples : search a number in a list or wait for a specific input.

In python the most important loop is "while", while a condition is met then the block of code inside of itself continue executing.

Syntax

example_number = 0

while example_number < 3 :

    print(example_number)

    example_number = example_number + 1

output : 
0
1
2

Useful when we dont know the exact number of iterations. If we have the number of iterations defined then "for" is better than while loop.
Example : count odd numbers in a list

for i in range (5):

    if i % 2 != 0:
        print(i)

output : 
1
3

Also exist "for each" with this loop is possible iterate in a list and the iterator will be each element.
Example: print each element of a list

example_list = ['house', 'apple', 1]

for element in example_list:
    print(element)

output : 
house
apple
1

Structured data in Python

Brayan Potosi — Tue, 29 Dec 2020 06:36:37 +0000

Some examples of structured data in Python are lists, sets, dictionaries, etc., its main feature is store a lot of items in a single variable.
Next i will to explain it with examples.

Lists : These can store different types of data and no matter if the elements are repited. It is represented with [ ], these are mutable it means that one list can change during execution.

List_items_example = [1, 'cat', 1.23]

if you want to get a specific item can access by index .

print(List_items_example[1])

output : cat

Sets : These are very used for store items which are not repeated, not is possible access to an element by index, it is represented with { }, these are immutable.

set_items_example = {'one', 'two',  3}

Dictionaries : These are different because each item is composed of one key and value, can access to a value by the key and no by index, these are mutable.

dict_items_example = {'fruit': 'apple', 'number': 33, 'char': 'Z'}

Getting a value

print(dict_items_example['fruit'])

output : apple

3 Useful libraries in python

Brayan Potosi — Fri, 18 Dec 2020 16:10:49 +0000

Sometimes we want resolve a specific problem like generate a random number, get the currently date, create ascii art, etc., if you have a problem probably already exist a library to resolve it.
Next i will mention some useful libraries

Pandas : That library is used for data science and business intelligence, it is the best for handling data and allow work with dataframes (two dimensional data structure)

Tkinter : Tkinter allow create a graphic interface for programs, a simple example is a calculator, python was not created for this porpouse but it is useful .

matplotlib : Maybe matplotlib is the most popular library, it is used mainly for data science purposes like create graphics, bars diagrams and different types of diagrams with few lines of code.

Functions in Python

Brayan Potosi — Sat, 12 Dec 2020 04:06:45 +0000

When we are coding usually see many task repited, that is not a problem but we will have a long code in the future, that can be not readeable or pretty.

For this reason the programing languages include functions, a function is a block of code that perform a especific task, this can receive one or more arguments and work with these for internal operations, all functions return a value.

Example :

user1_name = 'Juan'
user1_age = 23

user2_name = 'Pepe'
user2_age = 18

#Define function and parameters
def gretting(name, age): 
    #Task to perform
    print (f'Hi, your name is {name}')
    print (f'Hi, your age is {age}')

# call the function with 2 arguments (user1)
gretting(user1_name, user1_age) 
# call the function with 2 arguments (user2)
gretting(user2_name, user2_age) 


output : 

Hi, your name is Juan
Hi, your age is 23
Hi, your name is Pepe
Hi, your age is 18

Python String Methods

Brayan Potosi — Tue, 08 Dec 2020 20:02:46 +0000

Python has many build-in methods, these methods belong to a data-type now i will to explain the most common string methods

capitalize = this method returns some string but with the first character in uppercase.

my_string = 'random word'
capitalize_word = my_string.capitalize()
print(capitalize_word)

output : 'Random word'

lower = this method returns a copy of the string with all characters in lowercase.

my_string = 'Random WORD'
lower_word = my_string.lower()
print(lower_word)

output : 'random word'

upper = this method returns a copy of the string with all characters in uppercase.

my_string = 'Random WORD'
upper_word = my_string.upper()
print(upper_word)

output : 'RANDOM WORD'

swapcase() = this method change the characters , if the character is uppercase change for lowercase, does the same for the opposite case.

my_string = 'RANDOM word'
swap_word = my_string.swapcase()
print(swap_word)

output : 'random WORD'