update for some basic functions and common algorithms: dfs,bfs.

Signed-off-by: Jackey <smjjackey@sina.com>

Author: mjjackey

generator_fibonacci.py

@@ -0,0 +1,22 @@
+#!/usr/bin/python3
+import sys
+def fibonacci(n): # 生成器函数 - 斐波那契
+    """
+    在调用生成器运行的过程中，每次遇到 yield 时函数会暂停并保存当前所有的运行信息，
+    返回 yield 的值, 并在下一次执行 next() 方法时从当前位置继续运行。
+    :param n: the number of series
+    :return:
+    """
+    a, b, counter = 0, 1, 0
+    while True:
+        if (counter > n): return
+        yield a
+        a, b = b, a + b # a=b, b=a+b
+        counter += 1
+
+f = fibonacci(10) # f 是一个迭代器，由生成器返回生成
+while True:
+    try:
+        print(next(f), end=" ")
+    except StopIteration:
+        sys.exit()

iterator_filter_prime_numbers.py

@@ -27,10 +27,10 @@ def _not_divisible(n):
 
 def primes():
     yield 2
-    it = _odd_iter()
+    it = _odd_iter()  #### get a generator
     # print(it)  # one element: 2 and a generator object
     while True:
-        n = next(it)
+        n = next(it)  #### keep the whole generator: it
         yield n
         it = filter(_not_divisible(n), it)
 

list_clear.py

@@ -1,9 +1,32 @@
-lst1 = [1, 2, 3]
-lst2 = lst1
-del lst1[:]
-print(lst2) #[]
-del lst1
-# print(lst1) # error: name 'lst1' is not defined
-print(lst2) #[]
-del lst2
-print(lst2)  # error: name 'lst2' is not defined
+if __name__=="__main__":
+    lst1 = [1, 2, 3]
+    lst2 = lst1 ##### pass by reference
+    lst3 = lst1.copy()
+    # del lst1[:]
+    lst1.clear() ###### the same effect as del lst1[:]
+    print("lst1",lst1) #[]
+    print("lst2",lst2) ######[] pass by reference
+    print("lst3",lst3) #[1,2,3]
+    del lst1
+    try:
+        print(lst1) # error: name 'lst1' is not defined
+    except:
+        print("error")
+    print("lst2",lst2) ##############[]
+    print("lst3",lst3) #[1,2,3]
+    del lst2
+    try:
+        print(lst2)  # error: name 'lst2' is not defined
+    except:
+        print("error")
+    del lst3
+    try:
+        print(lst3)  # error: name 'lst3' is not defined
+    except:
+        print("error")
+
+    l1=[1,2,3]
+    l2=[1,2,3]
+    l3=[3,2,1]
+    print(l1==l2)
+    print(l1==l3)

list_set_try.py

@@ -37,6 +37,23 @@
     print("a和b中不同的元素")
     f = set(a).symmetric_difference(set(b))  # a和b中不同的元素
     print(f)
+    print()
+
+    # 定义一个集合
+    set1 = {1, 2, 3, 4, 5}
+    # 或者使用 set 函数
+    list1 = [6, 7, 7, 8, 8, 9]
+    set2 = set(list1)
+    set2.add(10)  # 添加新元素
+    print("set2",set2)  # set([6,7,8,9,10]) 去掉重复内容,
+    set2.update([10,11,12])
+    print("set2", set2)
+    try:
+        set3 = frozenset(list1)  # 固定集合
+        set3.add(10)  # 固定集合不能添加元素
+        print("set3",set3)
+    except:
+        print("error")
 
 
 

print.py

@@ -0,0 +1,11 @@
+
+if __name__ == "__main__":
+    PI = 3.141592653
+    print('%10.3f'%PI)
+
+    print("PI=%.*f" % (3, PI))
+    # 用*从后面的元组中读取字段宽度或精度,可以读取出来精度是3位
+    # PI=3.142
+    # 没有指定宽度，所以不需要缩进
+    print("PI=%*.3f" % (10, PI))  # 精度为3，总长为10.
+