add 04-generator-and-iterator README.md 💥

muyuuuu · muyuuuu · commit 7e1e2a0b8225 · 2021-01-08T21:39:55.000+08:00
diff --git a/04-generator-and-iterator/README.md b/04-generator-and-iterator/README.md
@@ -0,0 +1,3 @@
+1. `demo.py`：支持迭代的类，正向迭代与反向迭代
+2. `genitor.py`：生成器的类，用于迭代
+3. `iterator_visit.py`：迭代器的访问：如`islice`访问生成器指定起始和终止点，跳过指定位置的元素，元素的排列组合，迭代添加索引，同时迭代多个序列，`zip`合并序列的访问，`chain`不同数据在一起迭代访问，将列表展平
diff --git a/04-generator-and-iterator/genitor.py b/04-generator-and-iterator/genitor.py
@@ -18,28 +18,24 @@
 class linehistory:
     def __init__(self, lines, histlen=3):
         self.lines = lines
-        self.history = deque(maxlen=histlen)
 
     def __iter__(self):
         # 索引从 1 开始
         for lineno, line in enumerate(self.lines, 1):
-            self.history.append((lineno, line))
-            yield line
-
-    def clear(self):
-        self.history.clear()
+            yield lineno, line
 
 
 # 创建一个实例对象，可以访问内部属性值
 # 如果你在迭代操作时不使用for循环语句，那么你得先调用 iter() 函数
-with open('demo.py') as f:
+with open('demo.py', encoding='utf-8') as f:
     lines = linehistory(f)
-    for line in lines:
-        for lineno, hline in lines.history:
-            print('{}:{}'.format(lineno, hline), end='')
+    for lineno, line in lines:
+        print(lineno, ': ', line, end='')
+        # for lineno, hline in lines.history:
+            # print('{}:{}'.format(lineno, hline), end='')
 
 
-f = open('demo.py')
+f = open('demo.py', encoding='utf-8')
 lines = linehistory(f)
 t = iter(lines)
 print(next(t))
diff --git a/04-generator-and-iterator/iterator_visit.py b/04-generator-and-iterator/iterator_visit.py
@@ -35,16 +35,16 @@ def count(n):
 
 
 # 跳过可迭代对象的开始部分
-with open('/etc/passwd') as f:
-    # 去掉文件头部的行
-    for line in dropwhile(lambda line: not line.startswith('#'), f):
-    # 如下的写法会去掉注释行
-    # lines = (line for line in f if not line.startswith('#'))
-        print(line, end='')
+# with open('/etc/passwd') as f:
+#     # 去掉文件头部的行
+#     for line in dropwhile(lambda line: not line.startswith('#'), f):
+#     # 如下的写法会去掉注释行
+#     # lines = (line for line in f if not line.startswith('#'))
+#         print(line, end='')
 
 
 # 跳过指定位置的元素
-items = ['a', 'b', 'c', 1, 4, 10, 15]
+items = ['a', 'b', 'c', 1, 2, 4, 10, 15]
 # [3:] 和 [:3]
 for x in islice(items, 3, None):
     print(x)
@@ -57,16 +57,20 @@ def count(n):
 
 # 全部的排列组合
 for p in permutations(items):
-    print(p)
+    print(p,)
+print('--------')
 # 指定数量的排列组合
 for p in permutations(items, 2):
     print(p)
+print('--------')
 # 去除元素相同的排列组合（不考虑顺序）
 for i in combinations(items, 2):
     print(i)
+print('--------')
 # 元素被选取就会从候选中剔除掉, 就不会再考虑它
 for c in combinations_with_replacement(items, 3):
     print(c)
+print('--------')
 # 负责的迭代可以参考 itertools
 
 
@@ -112,7 +116,8 @@ def flatten(items, ignore_types=(str, bytes)):
 items = [1, 2, [3, 4, [5, 6], 7], 8]
 # Produces 1 2 3 4 5 6 7 8
 for x in flatten(items):
-    print(x)
+    # sep=':' 不行，只有一个输出
+    print(x, end=', ')
 items = ['Dave', 'Paula', ['Thomas', 'Lewis']]
 for x in flatten(items):
     print(x)

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+1. `demo.py`：支持迭代的类，正向迭代与反向迭代
	`2`	+2. `genitor.py`：生成器的类，用于迭代
	`3`	+3. `iterator_visit.py`：迭代器的访问：如`islice`访问生成器指定起始和终止点，跳过指定位置的元素，元素的排列组合，迭代添加索引，同时迭代多个序列，`zip`合并序列的访问，`chain`不同数据在一起迭代访问，将列表展平