merge from 3.1

Doc/library/csv.rst

@@ -419,21 +419,24 @@ Examples
 The simplest example of reading a CSV file::
 
    import csv
-   reader = csv.reader(open("some.csv", newline=''))
+   with open('some.csv', newline='') as f:
+       reader = csv.reader(f)
        for row in reader:
            print(row)
 
 Reading a file with an alternate format::
 
    import csv
-   reader = csv.reader(open("passwd"), delimiter=':', quoting=csv.QUOTE_NONE)
+   with open('passwd') as f:
+       reader = csv.reader(f, delimiter=':', quoting=csv.QUOTE_NONE)
        for row in reader:
            print(row)
 
 The corresponding simplest possible writing example is::
 
    import csv
-   writer = csv.writer(open("some.csv", "w"))
+   with open('some.csv', 'w') as f:
+       writer = csv.writer(f)
        writer.writerows(someiterable)
 
 Since :func:`open` is used to open a CSV file for reading, the file
@@ -442,7 +445,8 @@ encoding (see :func:`locale.getpreferredencoding`).  To decode a file
 using a different encoding, use the ``encoding`` argument of open::
 
    import csv
-    reader = csv.reader(open("some.csv", newline='', encoding='utf-8'))
+   with open('some.csv', newline='', encoding='utf-8') as f:
+       reader = csv.reader(f)
        for row in reader:
            print(row)
 
@@ -453,13 +457,15 @@ Registering a new dialect::
 
    import csv
    csv.register_dialect('unixpwd', delimiter=':', quoting=csv.QUOTE_NONE)
-   reader = csv.reader(open("passwd"), 'unixpwd')
+   with open('passwd') as f:
+       reader = csv.reader(f, 'unixpwd')
 
 A slightly more advanced use of the reader --- catching and reporting errors::
 
    import csv, sys
-   filename = "some.csv"
-   reader = csv.reader(open(filename, newline=''))
+   filename = 'some.csv'
+   with open(filename, newline='') as f:
+       reader = csv.reader(f)
        try:
            for row in reader:
                print(row)