Updates 20170628.md

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20170627.md

@@ -36,8 +36,6 @@ print(list(range(9, -1, -1)))
 
 \[9, 8, 7, 6, 5, 4, 3, 2, 1, 0\]
 
-
-
 Make the loop print the numbers from 0 to 19 instead of 0 to 9.
 
 ```python
@@ -93,12 +91,10 @@ hobbies = []
 for x in range(0,3):
     newhobbies = raw_input("your new hobbies")
     hobbies.append(str(newhobbies))
-    
+
 print hobbies
 ```
 
-
-
 ```python
 n = [[1, 2], [4, 5, 6, 7]]
 def flatten(lists):
@@ -191,8 +187,6 @@ else:
     print "You win!"
 ```
 
-
-
 猜數字遊戲
 
 ```python
@@ -211,8 +205,6 @@ else:
     print "You lose."
 ```
 
-
-
 取代
 
 ```python
@@ -228,8 +220,6 @@ print s
 
 X bird in the hand...
 
-
-
 The`,`character after our
 
 `print`statement means that our next`print`
@@ -249,6 +239,208 @@ print
 
 X bird in the hand...
 
+---
+
+### For/else
+
+Just like with`while`,`for`loops may have an`else`associated with them.
+
+```python
+fruits = ['banana', 'apple', 'orange', 'tomato', 'pear', 'grape']
+print 'You have...'
+for f in fruits:
+    if f == 'tomato':
+        print 'A tomato is not a fruit!' 
+        break #到tomato就會停止
+    print 'A', f
+else:
+    print 'A fine selection of fruits!'
+```
+
+You have...
+
+A banana
+
+A apple
+
+A orange
+
+A tomato is not a fruit!
+
+```python
+#沒有break的版本
+fruits = ['banana', 'apple', 'orange', 'tomato', 'pear', 'grape']
+print 'You have...'
+for f in fruits:
+    if f == 'tomato':
+        print 'A tomato is not a fruit!' 
+    print 'A', f
+else:
+    print 'A fine selection of fruits!'
+```
+
+You have...
+
+A banana
+
+A apple
+
+A orange
+
+A tomato is not a fruit!
+
+A tomato
+
+A pear
+
+A grape
+
+A fine selection of fruits!
+
+---
+
+Looping over a dictionary
+
+```python
+d = {'a': 'apple', 'b': 'berry', 'c': 'cherry'}
+for key in d:
+    # Your code here!
+    #if d[key] == 'berry':
+    print key, d[key]
+```
+
+a apple
+
+b berry
+
+c cherry
+
+---
+
+### 內建函數enumerate\(\)
+
+`enumerate`works by supplying a corresponding index to each element in the list that you pass it. Each time you go through the loop,
+
+`index`will be one greater, and`item`will be the next item in the sequence. It's very similar to using a normal`for`loop with a list, except this gives us an easy way to count how many items we've seen so far
+
+```python
+choices = ['pizza', 'pasta', 'salad', 'nachos']
+print 'Your choices are:'
+for index, item in enumerate(choices):
+    print index+1, item
+    # index從0開始所以+1
+```
+
+Your choices are:
+
+1 pizza
+
+2 pasta
+
+3 salad
+
+4 nachos
+
+---
+
+### 內建函數zip\(\)
+
+`zip`will create pairs of elements when passed two lists, and will stop at the end of the shorter list.`zip`can handle three or more lists as well!
+
+```python
+#zip()用來混合list_a & list_b
+list_a = [3, 9, 17, 15, 19]
+list_b = [2, 4, 8, 10, 30, 40, 50, 60, 70, 80, 90]
+for a, b in zip(list_a, list_b):
+    # Add your code here!
+    #print a,b 列出ab 
+    if a > b: #a,b比大小
+        print a
+    else:
+        print b
+```
+
+3
+
+9
+
+17
+
+15
+
+30
+
+---
+
+### 內建函數sum\(\) , float\(\)
+
+```py
+grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
+def grades_sum(scores):
+    total = sum(scores) 
+    #sum 自動總和
+    return total
+
+def grades_average(scores):
+    return grades_sum(scores)/float(len(scores))
+    #float轉換成浮點數
+    #len()長度（list數量）
+print grades_average(grades)
+```
+
+---
+
+Standard Deviation:
+
+The standard deviation is the square root of the variance.
+
+```python
+grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
+
+# all the grades
+def print_grades(grades):
+    for grade in grades:
+        print grade
+# sum of grades        
+def grades_sum(grades): 
+    total = 0
+    for grade in grades: 
+        total += grade
+    return total
+# average of grades
+def grades_average(grades):
+    sum_of_grades = grades_sum(grades)
+    average = sum_of_grades / float(len(grades))
+    return average
+# variance of grades
+def  grades_variance(scores):
+    average = grades_average(scores)
+    variance = 0
+    for score in scores:
+        variance += (average - score) ** 2
+        result = variance/float(len(scores))
+    return result 
+# deviation of grades
+def grades_std_deviation(variance):
+    return variance ** 0.5 #開根號
+
+variance = grades_std_deviation(grades_variance(grades))
+#取得variance的值再計算deviation
+print (variance)
+```
+
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