From: tutor-bounces+ramit.prasad=jpmchase....@python.org [mailto:tutor-bounces+ramit.prasad=jpmchase....@python.org] On Behalf Of eize...@gmail.com Sent: Wednesday, June 08, 2011 3:11 PM To: tutor@python.org Subject: [Tutor] String formatting question with 's'.format()
I'm working through the 'Learn Python' book by Mark Lutz, in this example: >>> somelist = list('SPAM') >>> parts = somelist[0], somelist[-1], somelist[1:3] >>> 'first={0}, last={1}, middle={2}'.format(*parts) "first=S, last=M, middle=['P', 'A']" why do we need the '*' at 'parts'. I know we need it, because otherwise it gives an error: Traceback (most recent call last): File "<pyshell#17>", line 1, in <module> 'first={0}, last={1}, middle={2}'.format(parts) IndexError: tuple index out of range Still, wouldn't python basically see 'parts' and insert the actual tuple instead of the variable 'parts'? How does the machine think? ======================== When you use {0} and {1} and {2} it looks for 3 variables being passed into it format. Passing *parts tells Python that parts is NOT an argument but instead a list of arguments. *parts is equivalent to 3 variables where: Variable 1 = 'S' Variable 2 = 'M' Variable 3 = ['P', 'A'] The error you see when using parts instead of *parts is basically saying it is looking for 2 more arguments to be passed into the function so that it can replace it. Compare: >>> 'first={0}'.format(parts) "first=('S', 'M', ['P', 'A'])" >>> 'first={0}'.format(*parts) 'first=S' Ramit Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology 712 Main Street | Houston, TX 77002 work phone: 713 - 216 - 5423 This communication is for informational purposes only. It is not intended as an offer or solicitation for the purchase or sale of any financial instrument or as an official confirmation of any transaction. All market prices, data and other information are not warranted as to completeness or accuracy and are subject to change without notice. Any comments or statements made herein do not necessarily reflect those of JPMorgan Chase & Co., its subsidiaries and affiliates. This transmission may contain information that is privileged, confidential, legally privileged, and/or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is STRICTLY PROHIBITED. Although this transmission and any attachments are believed to be free of any virus or other defect that might affect any computer system into which it is received and opened, it is the responsibility of the recipient to ensure that it is virus free and no responsibility is accepted by JPMorgan Chase & Co., its subsidiaries and affiliates, as applicable, for any loss or damage arising in any way from its use. If you received this transmission in error, please immediately contact the sender and destroy the material in its entirety, whether in electronic or hard copy format. Thank you. Please refer to http://www.jpmorgan.com/pages/disclosures for disclosures relating to European legal entities. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor