第一階段複習

--- tags: Sprout type: slide --- # 第一階段複習 siriuskoan --- ## Outline - 變數與型別 - 邏輯判斷 `if` - 迴圈 `for`、`while` - string - `list` - `dict` - 函式 - module --- ## 先複習一下 IO ```python= name = input("輸入名字: ") print("Your name is", name, sep=" ", end="!") ``` --- ## 變數與型別變數是存放值的容器型別代表這個變數(值)的類型 ---- ## 型別 - `int` - `str` - `float` - `list` - ... ---- ## 運算子 - `+`、`-`、`*`、`/`、`//` - `&`、`|`、`^`、`~` - `and`、`or`、`not` ---- ## 範例 ```python= # int a = 1 a2 = a + 5 a3 = a2 * 2 # float b = 1.0 # str c = str(a) c *= 10 # list d = [1, "1"] ``` ---- ## Quiz *階段考不會出現* What's the output? ```python= a = 12 a = str(a) a1 = int(a) + 1 a2 = a * 2 a3 = int(a) + 3 // 2 print(a1, a2, a3) print(type(a1), type(a2), type(a3)) ``` --- ## 邏輯判斷 `if` 判斷一個條件是否為真，並根據結果做不同的事情 ---- ## 範例 ```python= score = int(input("輸入分數: ")) if score >= 90: print("A+") elif score >= 85: print("A") elif score >= 80: print("A-") else: print("no A") ``` ---- ## `=` vs. `==` - `=` - 賦值 - 把一個變數的值設定成某個值 - `==` - 判斷 - 判斷兩個值是不是相同 ---- ## Quiz What's the output? ```python= # credit to 鄧人豪 x = 2 y = 3 bool1 = x == y bool2 = x = y print(bool1, bool2) print(x, y) ``` --- ## 迴圈 `for`、`while` 在某個條件成立時重複執行特定片段的程式 - `while` - 通常在有一個確定條件來決定是否要迴圈時使用 - 如: `name == ""` - `for` - 通常在確定(常數或是變數都可以)要跑幾次的時候使用 - 如: 倒數計時器 ---- ## 範例 ```python= # while name = input("請輸入名字: ") while name == "": print("名字不得為空") name = input("請輸入名字: ") print("Welcome, " + name) ``` ---- ## 範例 ```python= # for import time count = int(input("從多少開始倒數: ")) for i in range(count, -1, -1): print("倒數到: " + str(count)) time.sleep(1) print("倒數結束") ``` ---- ## 迴圈控制 - `break` - 直接中斷現在的**整個**迴圈 - `continue` - 跳過現在正在進行的**這一次**迴圈 ---- ## 範例 ```python= name = input("請輸入名字: ") while True: print("名字不得為空") name = input("請輸入名字: ") if name != "": break print("Welcome, " + name) ``` ---- ## 範例 - `range` 左閉右開 ```python= MAX = 0 for n in range(10): n = int(input("輸入 0 ~ 100 的數字: ")) if n > 100 or n < 0: print("範圍錯誤") continue MAX = max(MAX, n) print("最大值是 " + str(MAX)) ``` ---- ## 巢狀迴圈 ```python= for i in range(1, 10): for j in range(1, 10): print(f"{i}*{j}={i*j}", end=" ") print() ``` ---- ## Quiz 輸出 0 到 1 的每個小數，取到小數點後第二位即，$0.00,0.01,0.02,...,0.99,1.00$ ---- ### Ans ```python= for i in range(0, 101): print("%.2f" % round(i / 100, 2)) ``` --- ## String 一大堆字連在一起 ---- ## 範例 ```python= s1 = "abc" s2 = 'abc' s3 = """abc 123""" ``` ---- ## 字串格式化 ```python= name = "siriuskoan" print("My name is {}".format(name)) print(f"My name is {name}") ``` ---- ## 字串操作 ```python= string = "I love cat" # 長度 print(len(string)) # 索引 print(string[2]) # 分割 print(string[2:6]) ``` ---- ## 字串處理函式 ```python= string = "I love dog" # replace print(string.replace("dog", "cat")) # find dog_index = string.find("dog") print(f"The word dog is at {dog_index} to {dog_index + 2}") # split data = "Shohei Ohtani,57,17,.298".split(",") print(f"Player: {data[0]} AB: {data[1]} \ H: {data[2]}, AVG: {data[3]}") ``` ---- ## 字串處理函式 (cont.) ```python= # join like = ["Reading", "Coding", "Gaming"] print("I like " + ", ".join(like)) # strip name = input("名字: ") # name is " siriuskoan " print(name.strip()) ``` --- ## `list` 可以裝好幾項資料的資料結構 ---- ## 範例 ```python= li = [1, 2, 3] for ele in li: print(ele) # or for i in range(len(li)): print(li[i]) ``` ---- ## 分割 ```python= li = [1, 2, 3, 4, 5, 6, 7, 8, 9] print(li[0:5]) print(li[:-1]) print(li[::-1]) ``` ---- ## 串列操作 ```python= li = [1, 2, 3, 4, 5] li.append(6) li.extend([7, 8]) li.insert(0, 0) print(li.index(3)) print(li.count(1)) li.pop() li.remove(0) li.clear() ``` ---- ## 串列操作 (cont.) ```python= li = [2, 3, 9, 7, 6, 0] print(list(reversed(li))) li.reverse() print(sorted(li)) li.sort() ``` ---- ## `list` 的指派 ```python= L1 = [1, 2, 3, 4, 5] L2 = L1 L2[0] = -1 print(L1, L2) # 相同 ``` vs. ```python= L1 = [1, 2, 3, 4, 5] L2 = L1.copy() # or L1[:] L2[0] = -1 print(L1, L2) # 只有 L2 被改掉 ``` ---- ## `enumerate` ```python= li = [1, 2, 3, 4, 5] for index, value in enumerate(li): print(f"Index {index} is {value}") ``` ---- ## `map`、`filter` ```python= li = [-2, 2, 3, -10, 8, -7, 1] li = list(map(abs, li)) ``` ```python= li = [-2, 2, 3, -10, 8, -7, 1] def check_larger_than_zero(n): return True if n > 0 else False li = list(filter(check_larger_than_zero, li)) ``` --- ## `dict` 字典對鍵值對 (key-value pair) 做一對一的對應 key 必須要 immutable (不可變動) ---- ## 範例 ```python= d = {"name": "siriuskoan", "age": 19, "gender": "male"} print(d["name"]) # solve key error print(d.get("name")) # 更改值 d["name"] = "phkoan" # 新增 key d["department"] = "CS" # 刪除 key del d["gender"] ``` ---- ## `dict` 遍歷 ```python= d = {"name": "siriuskoan", "age": 19, "gender": "male"} for value in d.values(): print(value) for key in d.keys(): print(key) for k, v in d.items(): print(f"key {k} with value {v}") ``` ---- ## JSON ```python= import json json_data = """ {"name": "siriuskoan", "hobby": ["reading", "coding"]} """ d = json.loads(json_data) ``` --- ## Function 把一塊程式碼包起來，以利後續使用及功能區分 ---- ## 範例 ```python= def say_hello(name): print(f"Hello, {name}") def add(a, b, c = 0): return a + b + c ``` ---- ## Asterisks ```python= def add(*numbers): s = 0 for n in numbers: s += n return s def mapping(**kv): for k, v in kv.items(): print(f"{k}: {v}") ``` ---- ## Scope 會先從自己的 symbol table 找，找不到再去 global ```python= g = 10 def f(): print(g) g = 5 f() ``` ```python= g = 10 def f(): global g print(g) g = 5 f() ``` 建議變數用傳的，不要扯到一堆 global、local 的問題 ---- ## `lambda` 匿名函式 ```python= INPUT = "2139023, 3242, 34.2, 23, 43".split(", ") print(list(map(lambda x: int(x) ** 3 + 1, INPUT))) ``` ---- ## 遞迴自己呼叫自己注意終止條件及邊界處理 ```python= def fib(n): if n == 0 or n == 1: return 1 return fib(n - 1) + fib(n - 2) print(fib(10)) ``` --- ## Module 一整份 (可能是一個或多個 python 檔案) 可以讓你引用的程式 ---- ## `import` 引入 python 檔案或函式庫 ```python= import math print(math.sqrt(4)) import math as MATH print(MATH.sqrt(4)) from math import sqrt print(sqrt(4)) from math import sqrt as s print(s(4)) ``` ---- ## `import` 強烈建議不要用 `from module import *` 這種寫法 --- ## virtual environment 讓開發者可以針對不同專案獨立出不同開發環境的好幫手 ---- ## 使用安裝 `virtualenv` 套件 ```bash $ pip install virtualenv ``` 建立新的虛擬環境 ```bash $ virtualenv venv ``` 進入虛擬環境 ```bash $ .\venv\Scripts\activate ``` 這時候應該會看到 prompt 前面多出 `(venv)` ---- ## 使用進到去之後，就是一個完全與外部無關的環境了接著可以開始安裝需要的套件等等

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