create first context manager

context_manager/a.txt

@@ -0,0 +1,5 @@
+a
+da
+adawd
+cea
+wda adwa

context_manager/cm.py

@@ -0,0 +1,78 @@
+#Here write your imports
+import os
+from contextlib import contextmanager
+
+#
+def simple_open_and_write_without_context_manager(filename):
+    '''
+        Write simple code without context manager.
+        Dont forget to close.
+    '''
+    f = open(filename ,'w')
+    f.write('simple open and write done!')
+    f.close()
+
+def simple_open_and_write_with_context_manager(filename):
+    '''
+        Write your first simple context manager.
+        Use statmant with
+    '''
+    with open(filename, 'w') as f:
+        f.write('write with context manager done!')
+
+
+
+
+
+
+
+#### Using contextlib ####
+
+
+@contextmanager
+def open_file(file, mode):
+    f = open(file, mode)
+    yield f
+    f.close()
+
+def check_open_file(filename):
+    with open_file(filename, 'w') as f:
+        f.write('Lorem ipsum dolor sit amet, consectetur adipiscing elit.')
+    print(f.closed)
+
+
+#### CD Example ####
+def change_dir_without_context_manager(filename1, filename2):
+    cwd = os.getcwd()
+    os.chdir(filename1)
+    print(os.listdir())
+    os.chdir(cwd)
+
+    cwd = os.getcwd()
+    os.chdir(filename2)
+    print(os.listdir())
+    os.chdir(cwd)
+
+
+
+
+@contextmanager
+def change_dir(filename):
+    try:
+        cwd = os.getcwd()
+        os.chdir(filename)
+        yield
+    finally:
+        os.chdir(cwd)
+
+def try_change_dir(filename):
+    with change_dir(filename):
+        print(os.listdir())
+
+
+simple_open_and_write_without_context_manager('first.txt')
+simple_open_and_write_with_context_manager('second.txt')
+check_open_file('third')
+change_dir_without_context_manager('file_one','file_two')
+try_change_dir('file_one')
+try_change_dir('file_two')

context_manager/first.txt

@@ -0,0 +1 @@
+simple open and write done!

context_manager/readme.txt

@@ -0,0 +1,3 @@
+Context managers allow us to properly manage resources so that we can specify exactly what we want to set up and tear down when working with certain objects.
+we can tell that we are using context manager becouse of the with statemant.
+

context_manager/second.txt

@@ -0,0 +1 @@
+write with context manager done!

context_manager/third

@@ -0,0 +1 @@
+Lorem ipsum dolor sit amet, consectetur adipiscing elit.

context_manager/try.py

@@ -0,0 +1,3 @@
+with open('a.txt', 'r') as infile:
+    for line in infile:
+        print('> {}'.format(line))