学习递归函数以及切片的使用，学习slice和range内置的函数

dreamapplehappy · dreamapplehappy · commit 3c94f288d5a2 · 2017-07-30T23:08:24.000+08:00
diff --git a/day-07/range.py b/day-07/range.py
@@ -0,0 +1,12 @@
+# range 和 slice有点类似
+
+print(range(10)) # range(0, 10)
+
+print(list(range(10))) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+print(list(range(1, 10))) # [1, 2, 3, 4, 5, 6, 7, 8, 9]
+print(list(range(1, 10, 3))) # [1, 4, 7]
+
+
+# 第三个参数使用负数
+print(list(range(8, -16, -3))) # [8, 5, 2, -1, -4, -7, -10, -13]
+print(list(range(8, 16, -3))) # [] 注意 start和stop的顺序要和step表示的顺序一致
diff --git a/day-07/recursive-func.py b/day-07/recursive-func.py
@@ -0,0 +1,17 @@
+# 递归函数
+def factorial(n):
+    if n == 1:
+        return 1
+    return n * factorial(n-1)
+
+print(factorial(10))
+
+## 使用尾递归
+## @尾递归是指，在函数返回的时候，调用自身本身，并且，return语句不能包含表达式
+def tail_factorial(n, result):
+    if n == 1:
+       return result # 这里是关键的一步
+    return tail_factorial(n-1, n*result)
+
+print(tail_factorial(10, 1))
+print(factorial(10))
diff --git a/day-07/slice.py b/day-07/slice.py
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+# slice(start, stop, step)
+
+s_obj = slice(1, 3)
+
+nums = [1, 2, 3, 4, 5, 6]
+
+print(nums[s_obj]) # [2, 3]
+
+str = 'Hello,World'
+
+print(str[s_obj]) # el
+
+s_obj_1 = slice(-5, None, -2)
+print(str[s_obj_1]) # WolH
+
+s_obj_2 = slice(-5, -1, -2)
+print(type(str[s_obj_2])) # <class 'str'>
+print(str[s_obj_2] == '') # True
diff --git a/day-07/slicing.py b/day-07/slicing.py
@@ -0,0 +1,31 @@
+# 使用切片
+nums = [1, 2, 3, 4, 5, 6]
+print(nums[:]) #原来的nums的一个拷贝
+print(nums[:] is nums) # False
+print(nums[:] == nums) # True
+
+print(nums[1:3]) # [2, 3]
+print(nums[:3]) # [1, 2, 3]
+print(nums[1:5:2]) # [2, 4] 不包含6
+
+print(nums[-3:]) # [4, 5, 6]
+print(nums[-3:-1]) # [4, 5]
+print(nums[-3::2]) # [4, 6]
+print(nums[::-1]) # [6, 5, 4, 3, 2, 1]
+print(nums[::-2]) # [6, 4, 2]
+
+
+print(nums[-3::1]) # [4, 5, 6]
+
+print(nums[-3:]) # [4, 5, 6]
+print(nums[-3:-1]) # [4, 5]
+print(nums[-3::-1]) # [4, 3, 2, 1]
+print(nums[-1::-2]) # [6, 4, 2]
+
+print(nums[-1:-4:-2]) # [6, 4]
+
+## 最后一个参数表明了索引的递增顺序以及递增的增量
+
+print('Python'[-1:-4:-1])
+
+
