files of video 18 added

Author: MmahdiM79

video_18/while_loop.py

@@ -0,0 +1,100 @@
+from os import system
+system('clear')
+
+
+
+
+### why we need loops in programming
+# l = [1, 1.1, 'hello', True, 1+2j,
+#      'this world', 'this is a test', 'https://youtube.com/hello_world_media']
+# 
+# counter = 0
+# if isinstance(l[0], str) and len(l[0]) > 5:
+#     counter += 1
+# if isinstance(l[1], str) and len(l[1]) > 5:
+#     counter += 1
+# if isinstance(l[2], str) and len(l[2]) > 5:
+#     counter += 1
+# if isinstance(l[3], str) and len(l[3]) > 5:
+#     counter += 1
+# if isinstance(l[4], str) and len(l[4]) > 5:
+#     counter += 1
+# ...
+
+
+
+### while loop
+# l1 = [1, 1.1, 'hello', True, 1+2j,
+#      'this world', 'this is a test', 'https://youtube.com/hello_world_media']
+
+# counter = 0
+# i = 0
+# while i < len(l1):
+#     if isinstance(l1[i], str) and len(l1[i]) > 5:
+#         counter += 1
+#     i += 1
+
+# print(counter)
+
+
+### flow control
+# l2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+
+## break
+# i = 0
+# while i < len(l2):
+#     if l2[i] == 5:
+#         break
+#     print(l2[i])
+#     i += 1
+# print('end of the loop')
+
+## continue
+# i = 0  
+# while i < len(l2):
+#     if l2[i] < 5:
+#         i += 1
+#         continue
+#     print(l2[i])
+#     i += 1
+# print('end of the loop')
+
+
+### loop run time steps
+# '''
+#     l = [1, 2, ..., 10]
+#     i = 0
+#     while i < len(l):
+#         print(l[i])
+#         i += 1
+        
+#     runtime steps:
+#         step.1: check while condition
+#         step.2: execute the loop body
+#         step.3: increment i (usually)
+#         step.4: go to step.1
+# '''
+# # i = 0
+# # while i < -1:
+# #     print(i)
+# #     i += 1
+
+
+# ### else for while loop
+# l3 = [1, 2, 3, 4, 5, 6, 7]
+# i = 0
+# while i < len(l3):
+#     if l3[i] == 5:
+#         i += 1
+#         continue
+#         # break
+#     print(f'l3[{i}] = {l3[i]}')
+#     i += 1
+# else:
+#     # todo: do something
+#     print('end of the loop')
+
+
+### ifinite loop
+# while True:
+#     print('hello world', end=' ')