python

Referências dos slides e exercícios:

Exemplos

chmod +x hello_world.py

$ ./hello_world.py
Hello World

Números

Inteiros

num1 = 7
num2 = 42
total = num1 + num2

float

appx_pi = 22 / 7
area = 42.16
appx_pi + area

Notação Científica

sci_num1 = 3.982e5

String

str1 = 'hello'
str3 = "world"
print(str1 + str3)

Exemplos de operações

arithmetic operators
- + addition
- - subtraction
- * multiplication
- / division (float output)
- // division (integer output, result is not rounded)
- ** exponentiation
- % modulo
string operators
- + string concatenation
- * string repetition
comparison operators
- == equal to
- > greater than
- < less than
- != not equal to
- >= greater than or equal to
- <= less than or equal to
boolean logic
- and logical and
- or logical or
- not logical not
bitwise operators
- & and
- | or
- ^ exclusive or
- ~ invert bits
- >> right shift
- << left shift

def

#!/usr/bin/python3

# ----- function without arguments -----
def greeting():
    print("-----------------------------")
    print("         Hello World         ")
    print("-----------------------------")

greeting()

Argumentos

# ----- function with arguments -----
def sum_two_numbers(num1, num2):
    total = num1 + num2
    print("{} + {} = {}".format(num1, num2, total))

sum_two_numbers(3, 4)

# ----- function with return value -----
def num_square(num):
    return num * num

my_num = 3
print(num_square(2))
print(num_square(my_num))

Argumento Padrão

#!/usr/bin/python3

# ----- function with default valued argument -----
def greeting(style_char='-'):
    print(style_char * 29)
    print("         Hello World         ")
    print(style_char * 29)

print("Default style")
greeting()

print("\nStyle character *")
greeting('*')

print("\nStyle character =")
greeting(style_char='=')

>>> items = 15
>>> print("No. of items:", items)

>>> import sys
>>> print("Error!! Not a valid input", file=sys.stderr)
Error!! Not a valid input

Range

>>> range(5)
range(0, 5)

>>> list(range(5))
[0, 1, 2, 3, 4]

>>> list(range(-2, 2))
[-2, -1, 0, 1]

>>> list(range(1, 15, 2))
[1, 3, 5, 7, 9, 11, 13]

>>> list(range(10, -5, -2))
[10, 8, 6, 4, 2, 0, -2, -4]

type

>>> type(5)
<class 'int'>

>>> type('Hi there!')
<class 'str'>

>>> type(range(7))
<class 'range'>

>>> type(None)
<class 'NoneType'>

>>> type(True)
<class 'bool'>

>>> arr = list(range(4))
>>> arr
[0, 1, 2, 3]
>>> type(arr)
<class 'list'>

Escopo

#!/usr/bin/python3

def print_num():
    print("Yeehaw! num is visible in this scope, its value is: " + str(num))

num = 25
print_num()

$ ./variable_scope_1.py 
Yeehaw! num is visible in this scope, its value is: 25

#!/usr/bin/python3

def square_of_num(num):
    sqr_num = num * num

square_of_num(5)
print("5 * 5 = {}".format(sqr_num))

$ ./variable_scope_2.py 
Traceback (most recent call last):
  File "./variable_scope_2.py", line 7, in <module>
    print("5 * 5 = {}".format(sqr_num))
NameError: name 'sqr_num' is not defined

definindo variável global

#!/usr/bin/python3

def square_of_num(num):
    global sqr_num
    sqr_num = num * num

square_of_num(5)
print("5 * 5 = {}".format(sqr_num))

$ ./variable_scope_3.py
5 * 5 = 25

#!/usr/bin/python3

sqr_num = 4

def square_of_num(num):
    sqr_num = num * num
    print("5 * 5 = {}".format(sqr_num))

square_of_num(5)
print("Whoops! sqr_num is still {}!".format(sqr_num))

$ ./variable_scope_4.py 
5 * 5 = 25
Whoops! sqr_num is still 4!

Estruturas de controle

Combinação de testes

>>> num = 5
>>> num > 2
True
>>> num > 3 and num <= 5
True
>>> 3 < num <= 5
True
>>> num % 3 == 0 or num % 5 == 0
True

>>> fav_fiction = 'Harry Potter'
>>> fav_detective = 'Sherlock Holmes'
>>> fav_fiction == fav_detective
False
>>> fav_fiction == "Harry Potter"
True

Testando variáveis ou valores

>>> bool(num)
True
>>> bool(fav_detective)
True
>>> bool(3)
True
>>> bool(0)
False
>>> bool("")
False
>>> bool(None)
False

operador in

>>> def num_chk(n):
...     if n == 10 or n == 21 or n == 33:
...         print("Number passes condition")
...     else:
...         print("Number fails condition")
... 
>>> num_chk(10)
Number passes condition
>>> num_chk(12)
Number fails condition

operador in

>>> def num_chk(n):
...     if n in (10, 21, 33):
...         print("Number passes condition")
...     else:
...         print("Number fails condition")
... 
>>> num_chk(12)
Number fails condition
>>> num_chk(10)
Number passes condition

if

#!/usr/bin/python3

num = 45

# only if
if num > 25:
    print("Hurray! {} is greater than 25".format(num))

# if-else
if num % 2 == 0:
    print("{} is an even number".format(num))
else:
    print("{} is an odd number".format(num))

# if-elif-else
# any number of elif can be used
if num < 0:
    print("{} is a negative number".format(num))
elif num > 0:
    print("{} is a positive number".format(num))
else:
    print("{} is neither postive nor a negative number".format(num))

$ ./if_elif_else.py 
Hurray! 45 is greater than 25
45 is an odd number
45 is a positive number

if-else

#!/usr/bin/python3

num = 42

num_type = 'even' if num % 2 == 0 else 'odd'
print("{} is an {} number".format(num, num_type))

$ ./if_else_oneliner.py 
42 is an even number

for

#!/usr/bin/python3

number = 9
for i in range(1, 5):
    mul_table = number * i
    print("{} * {} = {}".format(number, i, mul_table))

while

#!/usr/bin/python3

# continuously ask user input till it is a positive integer
usr_string = 'not a number'
while not usr_string.isnumeric():
    usr_string = input("Enter a positive integer: ")

$ ./while_loop.py 
Enter a positive integer: abc
Enter a positive integer: 1.2
Enter a positive integer: 23
$

continue - pule o restante das instruções no loop (se houver) e o loop de saída

#!/usr/bin/python3

prev_num = 0
curr_num = 0
print("The first ten numbers in fibonacci sequence: ", end='')

for num in range(10):
    print(curr_num, end=' ')

    if num == 0:
        curr_num = 1
        continue

    temp = curr_num
    curr_num = curr_num + prev_num
    prev_num = temp

print("")

$ ./loop_with_continue.py 
The first ten numbers in fibonacci sequence: 0 1 1 2 3 5 8 13 21 34

break - pule o restante das instruções no loop (se houver) e sai do loop

#!/usr/bin/python3

import random

while True:
    # as with range() function, 500 is not inclusive
    random_int = random.randrange(500)
    if random_int % 4 == 0 and random_int % 6 == 0:
        break
print("Random number divisible by 4 and 6: {}".format(random_int))

while

$ ./loop_with_break.py 
Random number divisible by 4 and 6: 168
$ ./loop_with_break.py 
Random number divisible by 4 and 6: 216
$ ./loop_with_break.py 
Random number divisible by 4 and 6: 24

while e break

>>> while True:
         usr_string = input("Enter a positive integer: ")
         if usr_string.isnumeric():
             break
    
Enter a positive integer: a
Enter a positive integer: 3.14
Enter a positive integer: 1
>>>

lucascavalcante87 / python Goto Github PK

python's Introduction

python

Exemplos

Números

Inteiros

float

Notação Científica

String

Exemplos de operações

def

Argumentos

Argumento Padrão

Range

type

Escopo

Estruturas de controle

if

for

while

while e break

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