當程式越打越多時，我們可以把相同的程序打包成一個函式，就像是一個數學公式，會用他的話既節省空間、時間又美觀，看起來還會很電。

Function

def my_func(x):
    for i in range(x):
        print(i+1)
A = int(input("x = "))
my_func(A)

def greet(name):
 print("Hello, " + name + "!")
greet("Alice") # Output: "Hello, Alice!"
greet("Bob") # Output: "Hello, Bob!"

• return

def add(x, y):
    return x + y
result = add(10, 20) # result is now 30
print(result) # Output: 30

• default value

def greet(name, greeting="Hello"):
 print(greeting + ", " + name + "!")
greet("Alice") # Output: "Hello, Alice!"
greet("Bob", "Hi") # Output: "Hi, Bob!"

Function 練習題

Circle Area Calculation

import math
1. 編寫⼀個計算圓⾯積的函數。該函數應將圓的半徑作為參數並返回⾯積。
def circle_area(radius):
 return math.pi * radius**2
# Test the function
print(circle_area(2)) # Output: 12.566370614359172
print(circle_area(5)) # Output: 78.53981633974483

factorial

def factorial(num):
 result = 1
 for i in range(1, num+1):
 result *= i
 return result
# Test the function
print(factorial(5)) # Output: 120
print(factorial(10)) # Output: 3628800

反轉字串 reversed string

def reverse_string(s):
 return s[::-1]
# Test the function
print(reverse_string("hello")) # Output: "olleh"
print(reverse_string("world")) # Output: "dlrow"

質數判斷 Prime number judgment

def is_prime(num):
 if num < 2:
 return False
 for i in range(2, num):
 if num % i == 0:
 return False
 return True
# Test the function
print(is_prime(2))

Python .py Files

• 建立新檔案: my_functions.py

def greet(name):
 print("Hello, " + name + "!")
def add(x, y):
 return x + y

• import...

# Import all functions from my_functions.py
import my_functions
my_functions.greet("Sherry") # Output: "Hello, Sherry!"
result = my_functions.add(10, 50) # result is now 60
print(result) # Output: 60

or

• from...import...

# Import only the greet function from my_functions.py
from my_functions import greet
greet("Sasaki") # Output: "Hello, Sasaki!"

有時候遇到套件名稱一樣的話我們很容易搞混，所以可以使用as進行改名

• from...import...as(改名)...

# Import only the greet function from my_functions.py and give it a different
name
from my_functions import greet as say_hello
say_hello("Romain") # Output: "Hello, Romain!"

Python called 3rd party library（第三⽅庫）

我們可以在終端機下達一些指令已安裝套件或是檢查版本等等

• 檢查是否安裝 Python

python --version

• 安裝 Python 和 pip 後，可以使用以下命令安裝包

pip install (package_name)

• 檢查所有已安裝套件

pip list

• 檢查指定套件

pip show (套件名)

• pip 更新套件

pip install --upgrade package_name

• pip 刪除套件

pip uninstall package_name

• Google Codelab
  開頭要加!

!ls =>/content