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+---
+title: Python 初学笔记
+created: 2023-09-04
+summary: Note of 《Python As Fast as Possible - Learn Python in ~75 Minutes》
+tags: 
+  - 笔记
+  - Python
+---
+教程：[Python As Fast as Possible - Learn Python in ~75 Minutes](https://www.youtube.com/watch?v=VchuKL44s6E)
+
+- [GitHub - kyclark/tiny\_python\_projects: Code for Tiny Python Projects (Manning, 2020, ISBN 1617297518). Learning Python through test-driven development of games and puzzles.](https://github.com/kyclark/tiny_python_projects)
+
+## 交互式
+输入
+```bash
+python3
+```
+看到prompt提示符`>>>`  就进入交互模式了
+
+-  `<Control>`-`P `(previous) 
+- `<Control>`-`N` (next). 
+- `<Control>`-`D` exits a session
+
+- 工具：
+	- [Project Jupyter | Home](https://jupyter.org)
+- 教程：
+	- [practical python](https://dabeaz-course.github.io/practical-python/)
+	- [PEP 20 – The Zen of Python | peps.python.org](https://peps.python.org/pep-0020/)
+- 书籍
+	- [[流畅的Python]]
+
+## 数据类型
+- Int
+- Float
+- String
+- Bool
+
+## Arithmetic Operator
+- will always reture a float number
+	- `int(x/y)` => int
+- 幂运算： `x ** y` => `2**3 = 8`
+- 开跟号：`x //y` => `10 // 3 ` => 3 因为返回的是int，会自动取整
+- 求余 `x % y`
+
+## String Method
+- `.upper()`
+- `.lower()`
+- `.capitalize()`
+	- 首字大写
+- `.count()`
+	- `'Hello'.count('ll) = 2`
+- mutiply strings
+	- `'hello' * 3 = 'hellohellohello`
+	- `'hello' + 'yes' = 'helloyes`
+- `.replace()`
+- `.split()` 分割
+	- 和JS中[[split]]的区别：
+		- 当split里面没有任何参数的时候，JS中会将字符串切割成单个字符
+		- 而Python会按照空格分割（By default any whitespace is a separator[^1]）
+## Conditional Operators
+return -> `True` / `False`
+- ==
+- !=
+- `>=`
+- `<=`
+- `>`
+- `<`
+
+- 可以比较字符串，通过比较ASCI码
+	- `.orc('a')` 求得某个字符串的ASCI值
+	- 如果有几个字符串的话，逐一比较
+
+## Chained Conditionals
+- and 
+- or
+- not
+- order
+	1. nor
+	2. and
+	3. or
+
+## If/Else/Elif
+```py
+if x == 'Tim':
+	print('You are great')
+elif x == 'joe':
+	print('Bye joe!')
+else: 
+	print('No')
+```
+
+js
+```js
+if(x === 'tim') {
+	console.log('You are great')
+} else if (x === 'joe') {
+	console.log('Bye joe!')
+} else {
+	console.log('No')
+}
+```
+
+## List/Tuples
+- List
+	- 类似JS中的 [[数组|array]]
+	- `.list()`
+	- `x = [4, True, 'hi']` 
+	- `x[index]`
+	- `.len()`
+		- 返回长度
+		- string also works
+	- `.append()` 
+		- 在末尾加值
+	- `.extend([])`
+		- 扩展数组，在末尾加值
+	- `.pop(index)`
+		- remove the last element and return it 
+	- list is mutable
+	- deepcopy
+		- `y = x[:]
+- tuples
+	- TS中的 tuple
+	- immutable
+	- `y = (1,2,3,5)`
+- nesting
+	- `x=[[],(),[]]`
+
+## for loops
+```py
+for i in range(10)
+	print(i)
+
+x = [1,2,3,5,67]
+for i in range(len(x))
+	print(x[i])
+
+for i,element in enumerate(x):
+	print(i,element)
+// 0 1
+// 1 2
+// 2 3
+// 3 5
+// 4 67
+```
+
+- `.range()`
+	- arguments:
+		- stop
+		- start, stop
+		- start, stop, end
+	- not includes start and stop
+- `enumerate`
+	- enumerate()是Python中的一个内置函数,用于将一个可迭代对象(如列表、元组或字符串)组合为一个索引序列,同时列出数据和数据下标,一般用在for循环当中
+
+## While
+```bash
+while True:
+	print('run')
+	i += 1
+```
+
+## Slice
+切割数组
+```py
+x = [0,1,2,3,4,5,6,7,8]
+slice = x[0,4,2]
+// slice = [0,2]
+```
+- `slice = x[start:stop:step]`
+	- `x[:stop]`
+	- `x[start:]`
+	- `x[start:stop]`
+	- step默认为1
+	- reverse a list: `x[::-1]`
+
+## Sets
+unorder unique list
+```py
+x = set()
+s = { 2,3,4,5 } //set
+s2 = { 6 }
+s = { } // dict
+print( 4 in s) => boolean
+print(s.union(s2)) // => {2,3,4,5,6}
+```
+- `.add()`
+- `.remove()`
+- `.union`：合并set
+- `.difference`：比较差异
+- `.intersection`： 交集
+
+## Dicts
+```py
+x = {'key': 4}
+x['key2'] = 5
+print( 'key' in x) // => True
+
+//删除
+del x['key']
+```
+- `.value()`
+	- 获取所有values
+- `.update()`[^2]
+	- update() 方法用于将一个字典的键值对更新到另一个字典中。
+	- Update the dictionary with the key/value pairs from other, overwriting existing keys. Return None.
+	- update() accepts either another dictionary object or an iterable of key/value pairs (as tuples or other iterables of length two). If keyword arguments are specified, the dictionary is then updated with those key/value pairs: d.update(red=1, blue=2).
+
+## Comprehensions
+```py
+x = [ x for x in range(5)]
+x =[[0 for x in range(100)] for x in range(5)]
+x = { i for i in range(100) if i % 5 == 0 }
+```
+
+## Function
+
+```py
+def func(x,y,z=None):
+	print('Run',x,y,z)
+	return x * y , x /y 
+r1, r2 = func(10,5)
+func()
+```
+
+## Unpack Operator /* Args and ** Kwargs
+- `*x`
+- 类似于JS中的`...`
+- 用于list
+```py
+def fun(x,y):
+	print(x,y)
+
+pairs = [(1,2),(3,4)]
+for pair in pairs 
+	fun(*pair)
+```
+
+- `**x`
+- key word argumens
+- 用于dict
+```py
+def fun(x,y):
+	print(x,y)
+
+for(**{'x':2, 'y': 5})
+// 顺序不一也可以
+```
+
+## Scope & Globals
+- 函数内有局部作用域
+- 用`globel` 可以将局部变量变成全局变量
+```py
+def func():
+	global x
+	return x
+```
+
+
+## Exceptions
+- 意外事件，相当于JS中的`throw new Error('')`
+- 会打断程序的正常执行流程
+```py
+raise Exception('Bad')
+raise FileExistsError('')
+```
+常见的异常类型有:
+- StopIteration - 迭代器没有更多的值
+- ImportError - 导入模块失败
+- IndexError - 序列中找不到给定的索引
+- KeyError - 映射中找不到给定的键
+- ValueError - 传入无效的参数
+- TypeError - 对类型无效的操作
+- FileNotFoundError - 未找到文件
+- KeyboardInterrupt - 用户中断执行  
+## Handling Exceptions
+
+```py
+try: 
+	x = 7 /0
+expect Exception as e
+	print(e)
+finally:
+	print('finally')
+```
+
+##  Lambda
+lambda是Python中的匿名函数。它可以有多个参数,但只能有一个表达式。
+```py
+x = lambda x: x + 5
+```
+
+
+## Map and Filter
+- Map: 跟JS的[[map()]] 差不多
+- 返回map object
+```py
+x = [0,1,2,3,4,5,6,7,8]
+
+mp = map(lambda i : i +2 , x)
+// js : const mp = x.map((i)=> i+1)
+print(list(mp))
+
+mpf = filter(lambda i : i === 2 , x)
+
+```
+
+## F Strings
+- 类似于JS中的 [[template literal]] 
+```py
+tim = 89
+x = f'hello {6+8}'
+// js 
+// x = `hello ${6+8}`
+```
+
+
+## Buildin Functions
+- [[vars()]]
+
+[^1]: [Python String split() Method](https://www.w3schools.com/python/ref_string_split.asp)
+[^2]: [Built-in Types — Python 3.11.4 documentation](https://docs.python.org/3/library/stdtypes.html?highlight=update#dict.update)