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Hinet60613
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@ -6,7 +6,7 @@ contributors:
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- ["Andre Polykanine", "https://github.com/Oire"]
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- ["evuez", "http://github.com/evuez"]
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translators:
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- ["Michael Yeh", "https://github.com/hinet60613"]
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- ["Michael Yeh", "https://hinet60613.github.io/"]
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filename: learnpython.py
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lang: zh-tw
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---
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@ -255,137 +255,139 @@ li.index(7) # 7 不在串列中，造成 ValueError
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len(li) # => 6
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# Tuples are like lists but are immutable.
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# 元組(Tuple，以下仍用原文)類似於串列，但是它是不可改變的
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tup = (1, 2, 3)
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tup[0] # => 1
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tup[0] = 3 # Raises a TypeError
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tup[0] = 3 # 產生TypeError
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# You can do all those list thingies on tuples too
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# 能對串列做的東西都可以對tuple做
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len(tup) # => 3
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tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6)
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tup[:2] # => (1, 2)
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2 in tup # => True
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# You can unpack tuples (or lists) into variables
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a, b, c = (1, 2, 3) # a is now 1, b is now 2 and c is now 3
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d, e, f = 4, 5, 6 # you can leave out the parentheses
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# Tuples are created by default if you leave out the parentheses
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# 你可以把tuple拆開並分別將值存入不同變數
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a, b, c = (1, 2, 3) # a 現在是 1, b 現在是 2, c 現在是 3
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d, e, f = 4, 5, 6 # 也可以不寫括號
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# 如果不加括號，預設會產生tuple
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g = 4, 5, 6 # => (4, 5, 6)
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# Now look how easy it is to swap two values
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# 你看，交換兩個值很簡單吧
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e, d = d, e # d is now 5 and e is now 4
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# Dictionaries store mappings
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# 字典(Dictionary)用來儲存映射關係
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empty_dict = {}
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# Here is a prefilled dictionary
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# 你可以對字典做初始化
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filled_dict = {"one": 1, "two": 2, "three": 3}
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# Look up values with []
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# 用 [] 取值
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filled_dict["one"] # => 1
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# Get all keys as a list with "keys()"
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# 用 "keys()" 將所有的Key輸出到一個List中
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filled_dict.keys() # => ["three", "two", "one"]
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# Note - Dictionary key ordering is not guaranteed.
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# Your results might not match this exactly.
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# 註: 字典裡key的排序是不固定的
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# 你的執行結果可能與上面不同
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# 譯註: 只能保證所有的key都有出現，但不保證順序
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# Get all values as a list with "values()"
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# 用 "valuess()" 將所有的Value輸出到一個List中
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filled_dict.values() # => [3, 2, 1]
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# Note - Same as above regarding key ordering.
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# 註: 同上，不保證順序
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# Check for existence of keys in a dictionary with "in"
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# 用 "in" 來檢查指定的Key是否在字典中
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"one" in filled_dict # => True
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1 in filled_dict # => False
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# Looking up a non-existing key is a KeyError
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# 查詢不存在的Key會造成KeyError
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filled_dict["four"] # KeyError
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# Use "get()" method to avoid the KeyError
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# 用 "get()" 來避免KeyError
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# 若指定的Key不存在的話會得到None
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filled_dict.get("one") # => 1
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filled_dict.get("four") # => None
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# The get method supports a default argument when the value is missing
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# "get()" 函式支援預設值，當找不到指定的值時，會回傳指定的預設值
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filled_dict.get("one", 4) # => 1
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filled_dict.get("four", 4) # => 4
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# note that filled_dict.get("four") is still => None
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# (get doesn't set the value in the dictionary)
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# 注意此時 filled_dict.get("four") 仍然為 None
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# (get()此時並沒有產生出任何的值)
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# set the value of a key with a syntax similar to lists
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filled_dict["four"] = 4 # now, filled_dict["four"] => 4
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# 像操作list一樣，對指定的Key賦值
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filled_dict["four"] = 4 # 此時 filled_dict["four"] => 4
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# "setdefault()" inserts into a dictionary only if the given key isn't present
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filled_dict.setdefault("five", 5) # filled_dict["five"] is set to 5
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filled_dict.setdefault("five", 6) # filled_dict["five"] is still 5
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# "setdefault()" 只在指定的Key不存在時才會將值插入dictionary
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filled_dict.setdefault("five", 5) # filled_dict["five"] 被指定為 5
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filled_dict.setdefault("five", 6) # filled_dict["five"] 仍保持 5
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# Sets store ... well sets (which are like lists but can contain no duplicates)
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# 集合(Set)被用來儲存...集合。
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# 跟串列(List)有點像，但集合內不會有重複的元素
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empty_set = set()
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# Initialize a "set()" with a bunch of values
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some_set = set([1, 2, 2, 3, 4]) # some_set is now set([1, 2, 3, 4])
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# 初始化 "set()" 並給定一些值
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some_set = set([1, 2, 2, 3, 4]) # 現在 some_set 為 set([1, 2, 3, 4])，注意重複的元素只有一個會被存入
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# order is not guaranteed, even though it may sometimes look sorted
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another_set = set([4, 3, 2, 2, 1]) # another_set is now set([1, 2, 3, 4])
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# 一樣，不保證順序，就算真的有照順序排也只是你運氣好
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another_set = set([4, 3, 2, 2, 1]) # another_set 現在為 set([1, 2, 3, 4])
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# Since Python 2.7, {} can be used to declare a set
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# 從 Python 2.7 開始，可以使用大括號 {} 來宣告Set
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filled_set = {1, 2, 2, 3, 4} # => {1, 2, 3, 4}
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# Add more items to a set
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# 加入更多元素進入Set
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filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5}
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# Do set intersection with &
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# 用 & 來對兩個集合取交集
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other_set = {3, 4, 5, 6}
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filled_set & other_set # => {3, 4, 5}
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# Do set union with |
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# 用 | 來對兩個集合取聯集
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filled_set | other_set # => {1, 2, 3, 4, 5, 6}
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# Do set difference with -
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# 用 - 來將第二個集合內有的元素移出第一個集合
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{1, 2, 3, 4} - {2, 3, 5} # => {1, 4}
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# Do set symmetric difference with ^
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# 用 ^ 來對兩個集合取差集
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{1, 2, 3, 4} ^ {2, 3, 5} # => {1, 4, 5}
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# Check if set on the left is a superset of set on the right
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# 檢查左邊是否為右邊的母集
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{1, 2} >= {1, 2, 3} # => False
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# Check if set on the left is a subset of set on the right
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# 檢查左邊是否為右邊的子集
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{1, 2} <= {1, 2, 3} # => True
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# Check for existence in a set with in
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# 用 in 來檢查某元素是否存在於集合內
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2 in filled_set # => True
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10 in filled_set # => False
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####################################################
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## 3. Control Flow
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## 3. 控制流程
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####################################################
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# Let's just make a variable
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# 首先，先宣告一個變數
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some_var = 5
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# Here is an if statement. Indentation is significant in python!
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# prints "some_var is smaller than 10"
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# 這邊是 if 判斷式。注意，縮排對Python是很重要的。
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# 下面應該會印出 "some_var is smaller than 10"
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if some_var > 10:
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print "some_var is totally bigger than 10."
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elif some_var < 10: # This elif clause is optional.
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elif some_var < 10: # elif 可有可無
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print "some_var is smaller than 10."
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else: # This is optional too.
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else: # else 也可有可無
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print "some_var is indeed 10."
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"""
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For loops iterate over lists
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prints:
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For 迴圈會遞迴整的List
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下面的程式碼會輸出:
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dog is a mammal
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cat is a mammal
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mouse is a mammal
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"""
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for animal in ["dog", "cat", "mouse"]:
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# You can use {0} to interpolate formatted strings. (See above.)
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# 你可以用{0}來組合0出格式化字串 (見上面.)
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print "{0} is a mammal".format(animal)
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"""
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"range(number)" returns a list of numbers
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from zero to the given number
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prints:
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"range(number)" 回傳一個包含從0到給定值的數字List，
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下面的程式碼會輸出:
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0
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1
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2
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@ -395,9 +397,9 @@ for i in range(4):
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print i
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"""
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"range(lower, upper)" returns a list of numbers
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from the lower number to the upper number
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prints:
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"range(lower, upper)" 回傳一個包含從給定的下限
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到給定的上限的數字List
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下面的程式碼會輸出:
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4
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5
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6
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@ -407,8 +409,8 @@ for i in range(4, 8):
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print i
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"""
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While loops go until a condition is no longer met.
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prints:
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While迴圈會執行到條件不成立為止
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下面的程式碼會輸出:
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0
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1
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2
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@ -417,62 +419,62 @@ prints:
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x = 0
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while x < 4:
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print x
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x += 1 # Shorthand for x = x + 1
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x += 1 # x = x + 1 的簡寫
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# Handle exceptions with a try/except block
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# 用try/except處理例外
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# Works on Python 2.6 and up:
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# 適用Python 2.6及以上版本
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try:
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# Use "raise" to raise an error
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# 用 "raise" 來發起例外
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raise IndexError("This is an index error")
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except IndexError as e:
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pass # Pass is just a no-op. Usually you would do recovery here.
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pass # 毫無反應，就只是個什麼都沒做的pass。通常這邊會讓你做對例外的處理
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except (TypeError, NameError):
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pass # Multiple exceptions can be handled together, if required.
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else: # Optional clause to the try/except block. Must follow all except blocks
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print "All good!" # Runs only if the code in try raises no exceptions
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finally: # Execute under all circumstances
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pass # 有需要的話，多種例外可以一起處理
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else: # else 可有可無，但必須寫在所有的except後
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print "All good!" # 只有在try的時候沒有產生任何except才會被執行
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finally: # 不管什麼情況下一定會被執行
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print "We can clean up resources here"
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# Instead of try/finally to cleanup resources you can use a with statement
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# 除了try/finally以外，你可以用 with 來簡單的處理清理動作
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with open("myfile.txt") as f:
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for line in f:
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print line
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####################################################
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## 4. Functions
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## 4. 函式
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####################################################
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# Use "def" to create new functions
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# 用 "def" 來建立新函式
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def add(x, y):
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print "x is {0} and y is {1}".format(x, y)
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return x + y # Return values with a return statement
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return x + y # 用 "return" 來回傳值
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# Calling functions with parameters
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add(5, 6) # => prints out "x is 5 and y is 6" and returns 11
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# 用參數來呼叫韓式
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add(5, 6) # => 輸出 "x is 5 and y is 6" 並回傳 11
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# Another way to call functions is with keyword arguments
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add(y=6, x=5) # Keyword arguments can arrive in any order.
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# 你也可以寫上參數名稱來呼叫函式
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add(y=6, x=5) # 這種狀況下，兩個參數的順序並不影響執行
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# You can define functions that take a variable number of
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# positional args, which will be interpreted as a tuple if you do not use the *
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# 你可以定義接受多個變數的函式，這些變數是按照順序排序的
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# 如果不加*的話會被解讀為tuple
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def varargs(*args):
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return args
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varargs(1, 2, 3) # => (1, 2, 3)
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# You can define functions that take a variable number of
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# keyword args, as well, which will be interpreted as a dict if you do not use **
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# 你可以定義接受多個變數的函式，這些變數是按照keyword排序的
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# 如果不加**的話會被解讀為dictionary
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def keyword_args(**kwargs):
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return kwargs
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# Let's call it to see what happens
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# 呼叫看看會發生什麼事吧
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keyword_args(big="foot", loch="ness") # => {"big": "foot", "loch": "ness"}
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# You can do both at once, if you like
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# 如果你想要，你也可以兩個同時用
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def all_the_args(*args, **kwargs):
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print args
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print kwargs
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@ -482,39 +484,40 @@ all_the_args(1, 2, a=3, b=4) prints:
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{"a": 3, "b": 4}
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"""
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# When calling functions, you can do the opposite of args/kwargs!
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# Use * to expand positional args and use ** to expand keyword args.
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# 呼叫函式時，你可以做反向的操作
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# 用 * 將變數展開為順序排序的變數
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# 用 ** 將變數展開為Keyword排序的變數
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args = (1, 2, 3, 4)
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kwargs = {"a": 3, "b": 4}
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all_the_args(*args) # equivalent to foo(1, 2, 3, 4)
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all_the_args(**kwargs) # equivalent to foo(a=3, b=4)
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all_the_args(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=4)
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all_the_args(*args) # 等同於 foo(1, 2, 3, 4)
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all_the_args(**kwargs) # 等同於 foo(a=3, b=4)
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all_the_args(*args, **kwargs) # 等同於 foo(1, 2, 3, 4, a=3, b=4)
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# you can pass args and kwargs along to other functions that take args/kwargs
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# by expanding them with * and ** respectively
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# 你可以把args跟kwargs傳到下一個函式內
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# 分別用 * 跟 ** 將它展開就可以了
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def pass_all_the_args(*args, **kwargs):
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all_the_args(*args, **kwargs)
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print varargs(*args)
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print keyword_args(**kwargs)
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# Function Scope
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# 函式範圍
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x = 5
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def set_x(num):
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# Local var x not the same as global variable x
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# 區域變數 x 和全域變數 x 不是同一個東西
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x = num # => 43
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print x # => 43
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def set_global_x(num):
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global x
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print x # => 5
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x = num # global var x is now set to 6
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x = num # 全域變數 x 在set_global_x(6)被設定為 6
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print x # => 6
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set_x(43)
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set_global_x(6)
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# Python has first class functions
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# Python有一級函式
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def create_adder(x):
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def adder(y):
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return x + y
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@ -523,23 +526,23 @@ def create_adder(x):
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add_10 = create_adder(10)
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add_10(3) # => 13
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# There are also anonymous functions
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# 也有匿名函式
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(lambda x: x > 2)(3) # => True
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(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5
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# There are built-in higher order functions
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# 還有內建的高階函式
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map(add_10, [1, 2, 3]) # => [11, 12, 13]
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map(max, [1, 2, 3], [4, 2, 1]) # => [4, 2, 3]
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filter(lambda x: x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
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# We can use list comprehensions for nice maps and filters
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# 我們可以用List列表的方式對map和filter等高階函式做更有趣的應用
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[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
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[x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7]
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####################################################
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## 5. Classes
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## 5. 類別
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####################################################
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# We subclass from object to get a class.
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