Python 3 I/O - Revision history

Scott at 22:26, 13 November 2019

2019-11-13T22:26:15Z

← Older revision		Revision as of 22:26, 13 November 2019
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	More here: http://www.faqs.org/docs/diveintopython/kgp_commandline.html		More here: http://www.faqs.org/docs/diveintopython/kgp_commandline.html

			== Run a Command ==
			<source lang="python">
			command = "docker stats --no-stream"
			output = subprocess.run(command, shell=True, stdout=subprocess.PIPE).stdout.decode("utf-8")
			for line in output.splitlines():
			print(line)
			</source>

	== Reading and writing files ==		== Reading and writing files ==

Scott: /* print statement */

2014-01-14T17:53:09Z

print statement

← Older revision		Revision as of 17:53, 14 January 2014
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	print(spam, ham, end="") # Same, but don't add newline at end of text.		print(spam, ham, end="") # Same, but don't add newline at end of text.
	print(spam, ham, file=myfile) # Send text to myfile.write, not to sys.stdout.write.		print(spam, ham, file=myfile) # Send text to myfile.write, not to sys.stdout.write.
			print("There are <", 2**32, "> possibilities!", sep="") # There are <4294967296> possibilities!
	</source>		</source>

Scott: /* MySQL access */

2014-01-14T17:47:33Z

MySQL access

← Older revision		Revision as of 17:47, 14 January 2014
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	cursor.execute("select the_date, close from stocks where issue = 'a'")		cursor.execute("select the_date, close from stocks where issue = 'a'")
	for row in cursor.fetchall():		for row in cursor.fetchall():
	print row		print(row)
	cursor.close()		cursor.close()
	conn.close()		conn.close()

Scott: /* XML parsing example */

2014-01-14T17:47:13Z

XML parsing example

← Older revision		Revision as of 17:47, 14 January 2014
Line 149:		Line 149:
	parser.setContentHandler(handler)		parser.setContentHandler(handler)
	parser.parse('books.xml')		parser.parse('books.xml')
	print handler.mapping		print(handler.mapping)
	</source>		</source>

Scott: /* HTML parsing example */

2014-01-14T17:46:50Z

HTML parsing example

← Older revision		Revision as of 17:46, 14 January 2014
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	pieces = urlparse.urlparse(value)		pieces = urlparse.urlparse(value)
	if pieces[0] != 'http': return		if pieces[0] != 'http': return
	print urlparse.urlunparse(pieces)		print(urlparse.urlunparse(pieces))
	return		return

Scott: /* Formatted printing */

2014-01-14T17:46:09Z

Formatted printing

← Older revision		Revision as of 17:46, 14 January 2014
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	y = 3.14		y = 3.14
	z = "george"		z = "george"
	print 'result = %d' % x # prints: result = 42		print('result = %d' % x) # prints: result = 42
	print 'answers are: %d %f' % (x,y) # prints: answers are: 42 3.14		print('answers are: %d %f' % (x,y)) # prints: answers are: 42 3.14
	print 'hello %s' % z # prints: hello george		print('hello %s' % z) # prints: hello george
	</source>		</source>

Scott: /* print statement */

2014-01-14T17:45:07Z

print statement

← Older revision		Revision as of 17:45, 14 January 2014
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	== print statement ==		== print statement ==
	<source lang="python">		<source lang="python">
	print spam, ham # Print objects to sys.stdout; add a space between.		print(spam, ham) # Print objects to sys.stdout; add a space between.
	print spam, ham, # Same, but don't add newline at end of text.		print(spam, ham, end="") # Same, but don't add newline at end of text.
	print ~~>> myfile,~~ spam, ham # Send text to myfile.write, not to sys.stdout.write.		print(spam, ham, file=myfile) # Send text to myfile.write, not to sys.stdout.write.
	</source>		</source>

Scott: Created page with "== Command-line arguments == Command line arguments are placed in the list `sys.argv`. import sys command = sys.argv[0] firstArg = sys.argv[..."

2014-01-14T17:43:01Z

Created page with "== Command-line arguments == Command line arguments are placed in the list <code>sys.argv</code>. <source lang="python"> import sys command = sys.argv[0] firstArg = sys.argv[..."

New page

== Command-line arguments ==
Command line arguments are placed in the list <code>sys.argv</code>.
<source lang="python">
import sys

command = sys.argv[0]
firstArg = sys.argv[1]
secondArg = sys.argv[2]
</source>

There is also a <code>getopt</code> module.

More here: http://www.faqs.org/docs/diveintopython/kgp_commandline.html

== Reading and writing files ==
<source lang="python">
output = open('/tmp/spam', 'w') # Create output file ('w' means write).
input = open('data', 'r') # Create input file ('r' means read).
S = input.read( ) # Read entire file into a single string.
S = input.read(N) # Read N bytes (1 or more).
S = input.readline( ) # Read next line (through end-line marker).
L = input.readlines( ) # Read entire file into list of line strings.
output.write(S) # Write string S into file.
output.writelines(L) # Write all line strings in list L into file.
output.close( ) # Manual close (done for you when file collected).
</source>

== Manipulating files ==
See this page for more: http://docs.python.org/lib/os-file-dir.html
<source lang="python">
import os
os.access(fileName, os.F_OK) # returns True if file exists
os.access(fileName, os.R_OK) # returns True if file is readable
os.access(fileName, os.W_OK) # returns True if file is writeable
os.access(fileName, os.X_OK) # returns True if file is executable
os.getcwd() # return a path of current working directory
os.mkdir(newName) # create a directory
os.listdir(dirName) # directory listing
os.rename(oldName, newName) # move/rename a file
os.remove(fileName) # unlink a file
</source>

== Parsing a text file line-by-line ==
<source lang="python">
for line in file('/tmp/test/txt', 'r'):
do something with line, like
args = line.strip().split()
</source>

== print statement ==
<source lang="python">
print spam, ham # Print objects to sys.stdout; add a space between.
print spam, ham, # Same, but don't add newline at end of text.
print >> myfile, spam, ham # Send text to myfile.write, not to sys.stdout.write.
</source>

== Formatted printing ==
<source lang="python">
x = 42
y = 3.14
z = "george"
print 'result = %d' % x # prints: result = 42
print 'answers are: %d %f' % (x,y) # prints: answers are: 42 3.14
print 'hello %s' % z # prints: hello george
</source>

== urllib module for web access ==
<source lang="python">
import urllib

# open a url for reading
page = urlopen('http://www.python.org')
page.readline( ) # '<HTML>\012'
# download a page directly
urlretrieve('http://www.python.org/', 'wwwpython.html')
</source>

== HTML parsing example ==
<source lang="python">
# extracts urls from a web page
import HTMLParser, urllib, urlparse

class LinksParser(HTMLParser.HTMLParser):
def __init__(self):
HTMLParser.HTMLParser.__init__(self)
self.seen = {}
def handle_starttag(self, tag, attributes):
if tag != 'a': return
for name, value in attributes:
if name == 'href' and value not in self.seen:
self.seen[value] = True
pieces = urlparse.urlparse(value)
if pieces[0] != 'http': return
print urlparse.urlunparse(pieces)
return

p = LinksParser( )
f = urllib.urlopen('http://www.python.org/index.html')
BUFSIZE = 8192
while True:
data = f.read(BUFSIZE)
if not data: break
p.feed(data)

p.close( )
</source>

== XML parsing example ==
<source lang="xml">
<catalog>
<book isbn="1-56592-724-9">
<title>The Cathedral & the Bazaar</title>
<author>Eric S. Raymond</author>
</book>
<book isbn="1-56592-051-1">
<title>Making TeX Work</title>
<author>Norman Walsh</author>
</book>

</catalog>
</source>

<source lang="python">
import xml.sax, xml.sax.handler

class BookHandler(xml.sax.handler.ContentHandler):
def __init__(self):
self.inTitle = 0 # handle XML parser events
self.mapping = {} # a state machine model

def startElement(self, name, attributes):
if name == "book": # on start book tag
self.buffer = "" # save ISBN for dict key
self.isbn = attributes["isbn"]
elif name == "title": # on start title tag
self.inTitle = 1 # save title text to follow

def characters(self, data):
if self.inTitle: # on text within tag
self.buffer += data # save text if in title

def endElement(self, name):
if name == "title":
self.inTitle = 0 # on end title tag
self.mapping[self.isbn] = self.buffer # store title text in dict

parser = xml.sax.make_parser( )
handler = BookHandler( )
parser.setContentHandler(handler)
parser.parse('books.xml')
print handler.mapping
</source>

== MySQL access ==
http://www.kitebird.com/articles/pydbapi.html
<source lang="python">
import MySQLdb

conn = MySQLdb.connect(host = "localhost", user = "barney", passwd = "xxxxxx", db = "bts")
cursor = conn.cursor()
cursor.execute("select the_date, close from stocks where issue = 'a'")
for row in cursor.fetchall():
print row
cursor.close()
conn.close()
</source>

If using INNODB tables, you need to throw in a commit statement for the connection before closing it:
<source lang="python">
conn = MySQLdb.connect(host = "localhost", user = "barney", passwd = "xxxxxx", db = "schedule")
cursor = conn.cursor()
cursor.execute("insert into users (name, pass) values ('Herman', '2909e93f30ac902891093')")
cursor.close()
conn.commit() <== don't forget this!
conn.close()
</source>

== Windows Tip ==
When starting a command-line python script by clicking on it in Winodws, use the raw_input() function at the end to keep the window open. Hitting return will close it.

== Send E-mail ==
<source lang="python">
import smtplib
import os
from email.MIMEMultipart import MIMEMultipart
from email.MIMEBase import MIMEBase
from email.MIMEText import MIMEText
from email.Utils import COMMASPACE, formatdate
from email import Encoders

def sendMail(send_from, send_to, subject, text, files=[], server="localhost"):
assert type(send_to)==list
assert type(files)==list

msg = MIMEMultipart()
msg['From'] = send_from
msg['To'] = COMMASPACE.join(send_to)
msg['Date'] = formatdate(localtime=True)
msg['Subject'] = subject

msg.attach( MIMEText(text) )

for f in files:
part = MIMEBase('application', "octet-stream")
part.set_payload( open(file,"rb").read() )
Encoders.encode_base64(part)
part.add_header('Content-Disposition', 'attachment; filename="%s"' % os.path.basename(f))
msg.attach(part)

smtp = smtplib.SMTP(server)
smtp.sendmail(send_from, send_to, msg.as_string())
smtp.close()
</source>

Python 3 I/O - Revision history

Scott at 22:26, 13 November 2019

Scott: /* print statement */

Scott: /* MySQL access */

Scott: /* XML parsing example */

Scott: /* HTML parsing example */

Scott: /* Formatted printing */

Scott: /* print statement */

Scott: Created page with "== Command-line arguments == Command line arguments are placed in the list sys.argv. import sys command = sys.argv[0] firstArg = sys.argv[..."

Scott: Created page with "== Command-line arguments == Command line arguments are placed in the list `sys.argv`. import sys command = sys.argv[0] firstArg = sys.argv[..."