Built-in Functions

Basic Functions

print()
- 여러 인자를 받을 수 있고, 기본적으로 인자들을 스페이스로 구분하여 출력함

input()

name = input("Enter your name: ")

Basic Input

name = input("Enter your name: )
print(f"Hello, {name}!")

Numeric Input
- You can use input() to receive numeric input, but you need to convert the input to the desired data type (e.g., int or float).
```
age = int(input("Enter your age: "))
if age >= 18:
    print("Your are an adult.")
else:
    print("Your are a minor.")
```

Multiple Inputs:

name = input("Enter your name: ")
age = int(input("Enter your age: "))
print(f"Hello, {name}! You are {age} years old.")

Using input() in a Loop

while True:
    user_input = input("Enter 'quit' to exit: ")
    if user_input.lower() == 'quit':
        break

Handling Exceptions

try:
    age = int(input("Enter your age: ))
    print(f"You entered {age} yeaers old.")
except ValueError:
    print("Invalid input. Please enter a valid number.")

Using input() with eval()

expression = input("Enter a mathmatical expression: ")
result = eval(expression)

len(): returns the number of items in an object, such as a string, list, or tuple
```
length = len("Python")
```
type(): returns the type of an object
```
x = 5
t = type(x)
```
int(), float(), str(), list(), tuple(), dict(), set(): used for type conversion between different data types.
```
x = int("42")
y = str(3.14)
```
range(): generates a sequence of numbers within a specified range
```
numbers = list(range(1, 6))  # Generates [1, 2, 3, 4, 5]
```

sum(), max(), min(), abs(): perform mathematical operations on data

numbers = [1, 2, 3, 4, 5]
total = sum(numbers)
largest = max(numbers)

Advanced Functions

sorted(): returns a sorted version of a list, without modifying the original list.
```
numbers = [5, 2, 9, 1, 3]
sorted_numbers = sorted(numbers)
```

zip(): combines two or more iterables element-wise.

names = ["Alice", "Bob", "Charlie"]
scores = [85, 92, 78]
combined = list(zip(names, scores))

map(), filter(): used for functional programming operations on iterable data structures

numbers = [1, 2, 3, 4, 5]
squared = list(map(lambda x: x**2, numbers))
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))

all(), any(): check if all or any elements of an iterable evaluate to True

nums = [True, True, False, True]
all_true = all(nums)  # False
any_true = any(nums)  # True

open(): Used to open files for reading or writing.

with open("example.txt", "r") as file:
    content = file.read()

help(): Displays documentation and help for Python objects and modules.
```
help(list)
```
dir(): lists all attributes and methods of an object.
- the output of dir() can be quite extensive, especially for complex objects and modules
- includes both built-in methods and user-defined attributes and methods
- can use this function to discover what functionality is available for a particular object or module and to aid in debugging and exploration during development
```
dir(list)
```
1. Built-in Functions and Modules
  - can use dir() to explore the attributes and methods of built-in functions and modules
```
print(dir(len))  # List attributes and methods of the len function
import math
print(dir(math))  # List attributes and functions in the math module
```
2. Data Types
  - can use dir() to examine the methods and attributes available for various data types, such as strings, lists, and dictionaries.
```
s = "Hello, World!"
print(dir(s))  # List attributes and methods of a string

numbers = [1, 2, 3, 4, 5]
print(dir(numbers))  # List attributes and methods of a list
```
3. Custom Classes
  - when you define your own classes, you can use dir() to inspect the attributes and methods of instances of those classes.
```
class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

person = Person("Alice", 30)
print(dir(person))  # List attributes and methods of a custom class instance
```
4. Modules and Packages
  - dir() can also be used to explore modules and packages you create or import.
```
# Assuming you have a custom module named mymodule.py
import mymodule
print(dir(mymodule))  # List attributes and functions in your custom module
```
5. Objects with Special Methods:
  - Some objects, such as iterators and context managers, have special methods (e.g., iter, enter, exit) that you can inspect using dir().
```
numbers = [1, 2, 3, 4, 5]
iterator = iter(numbers)
print(dir(iterator))  # List special methods for an iterator
```
6. Built-in Types and Modules:
  - You can explore the attributes and methods of built-in types and modules, such as list, str, and math.
```
print(dir(list))  # List attributes and methods of the list type
print(dir(str))   # List attributes and methods of the str type
print(dir(math))  # List attributes and functions in the math module
```

eval(): used to dynamically evaluate a single Python expression (a piece of Python code that produces a value) from a string

Basic Mathematical Evaluation:

expression = "2 + 3 * 4"
result = eval(expression)
print(result)  # Output: 14

User Input Evaluation

expression = input("Enter a mathematical expression: ")
try:
    result = eval(expression)
    print("Result:", result)
except Exception as e:
    print("Error:", e)

map()
- 주어진 함수를 순회 가능한(iterable) 객체의 각 요소에 적용하여 새로운 순회 가능한 객체를 생성하는 함수
```
map(function, iterable, ...)
```
- function: 각 요소에 적용할 함수를 지정
- iterable: 함수를 적용할순회 가능한 객체를 지정. 여러 개의 iterable을 지정할 수 있으며, map()은 모든 iterable에서 동시에 요소를 가져와 함수를 적용함. iterable의 길이가 다를 경우 가장 짧은 iterable의 길이에 맞춰 처리됨
- 함수를 벡터화하고 반복적으로 적용하는 데 사용됨. 이를 통해 코드를 더 간결하게 만들고, 여러 값을 한 번에 변환하거나 처리하는 데 유용함
- map 함수는 결과를 즉시 계산하지 않고, 지연 평가(lazy evaluation)를 사용하여 요소를 계산하지 않고 기다림

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05. built-in functions.md

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Built-in Functions

Basic Functions

Advanced Functions

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Built-in Functions

Basic Functions

Advanced Functions