❝ FIXME ❞
— FIXME
-
FIXME -
FIXME + +
+open(..., encoding='...') +open(..., 'r', encoding='...') ++ +
FIXME + +
FIXME
Python has a built-in function, open(), for opening a file on disk. The open() function returns a file object, which has methods and attributes for getting information about and manipulating the file.
-
->>> image = open('examples/beauregard-100x100.jpg', 'rb')
->>> image
-<io.BufferedReader object at 0x00C7A390>
->>> image.mode
-'rb'
->>> image.name
-'examples/beauregard-100x100.jpg'
->>>
->>> f = open("/music/_singles/kairo.mp3", "rb") ①
->>> f ②
-<open file '/music/_singles/kairo.mp3', mode 'rb' at 010E3988>
->>> f.mode ③
-'rb'
->>> f.name ④
-'/music/_singles/kairo.mp3'
+
+
+Reading Data From A Text File
+
+FIXME
+
+
+
6.2.2. Closing Files
-Open files consume system resources, and depending on the file mode, other programs may not be able to access them. It's
- important to close files as soon as you're finished with them.
+
+
Open files consume system resources, and depending on the file mode, other programs may not be able to access them. It’s important to close files as soon as you’re finished with them.
+
+
+
+
FIXME checking if a file is closed
+
+
Using The with Statement
+
+FIXME "with open(...) as file" pattern
+
+
Reading Data One Line At A Time
+
+FIXME
+
+
FIXME what's a "line"? (line endings discussion, universal line endings, etc.)
+
+
Writing to Text Files
+
+FIXME
+
+
-
FIXME -
FIXME write(), writelines(), .writeable +
FIXME + +
FIXME + +
+>>> image = open('examples/beauregard-100x100.jpg', 'rb')
+>>> image
+<io.BufferedReader object at 0x00C7A390>
+>>> image.mode
+'rb'
+>>> image.name
+'examples/beauregard-100x100.jpg'
+
+
++>>> image +<io.BufferedReader object at 0x00C7A390> +>>> image.tell() +0 +>>> data = image.read(3) +>>> data +b'\xff\xd8\xff' +>>> image.tell() +3 +>>> image.seek(0) +0 +>>> data = image.read() +>>> len(data) +3150 ++ +
FIXME + + -<channel> -<title>Slashdot</title> -<link>http://slashdot.org/</link> -<description>News for nerds, stuff that matters</description> -</channel> - -<image> -<title>Slashdot</title> -<url>http://images.slashdot.org/topics/topicslashdot.gif</url> -<link>http://slashdot.org/</link> -</image> - -<item> -<title>To HDTV or Not to HDTV?</title> -<link>http://slashdot.org/article.pl?sid=01/12/28/0421241</link> -</item> - -[...snip...] -
urlopen takes a web page URL and returns a file-like object. Most importantly, this object has a read method which returns the HTML source of the web page.
-minidom.parse, which obediently calls the read method of the object and parses the XML data that the read method returns. The fact that this XML data is now coming straight from a web page is completely irrelevant. minidom.parse doesn't know about web pages, and it doesn't care about web pages; it just knows about file-like objects.
-urlopen gives you.
-
->>> contents = "<grammar><ref id='bit'><p>0</p><p>1</p></ref></grammar>"
->>> xmldoc = minidom.parseString(contents) ①
->>> print xmldoc.toxml()
-<?xml version="1.0" ?>
-<grammar><ref id="bit"><p>0</p><p>1</p></ref></grammar>
-minidom has a method, parseString, which takes an entire XML document as a string and parses it. You can use this instead of minidom.parse if you know you already have your entire XML document in a string.
-OK, so you can use the minidom.parse function for parsing both local files and remote URLs, but for parsing strings, you use... a different function. That means that if you want to be able to take input from a
-file, a URL, or a string, you'll need special logic to check whether it's a string, and call the parseString function instead. How unsatisfying.
-
If there were a way to turn a string into a file-like object, then you could simply pass this object to minidom.parse. And in fact, there is a module specifically designed for doing just that: StringIO.
+
- # try to open with native open function (if source is pathname)
- try:
- return open(source) ③
- except (IOError, OSError):
- pass
+
openAnything function takes a single parameter, source, and returns a file-like object. source is a string of some sort; it can either be a URL (like 'http://slashdot.org/slashdot.rdf'), a full or partial pathname to a local file (like 'binary.xml'), or a string that contains actual XML data to be parsed.
-urllib ever supports new types of URLs in the future, you will also support them without recoding. If urllib is able to open source, then the return kicks you out of the function immediately and the following try statements never execute.
-urllib yelled at you and told you that source wasn't a valid URL, you assume it's a path to a file on disk and try to open it. Again, you don't do anything fancy to check whether source is a valid filename or not (the rules for valid filenames vary wildly between different platforms anyway, so you'd probably get them wrong anyway). Instead, you just blindly open the file, and silently trap any errors.
-StringIO to create a file-like object out of it and return that. (In fact, since you're using the str function, source doesn't even need to be a string; it could be any object, and you'll use its string representation, as defined by its __str__ special method.)
-Now you can use this openAnything function in conjunction with minidom.parse to make a function that takes a source that refers to an XML document somehow (either as a URL, or a local filename, or a hard-coded XML document in a string) and parses it.
-