PEP (Python Enhancement Proposal)

Escape Sequences\' want print a postrophe\b won't print char before it ex:deleted lbother scape sequencesoutput:deleteIn - new lineIt - horizontal tu bulationIr - moves all Char after Ir to the beginningof the line, over writing as manycharacters as it movedif we need to print a back lash ( tsel fwe need to use 2!ex: print (iv) Slicing StringsMonty Python01234567891011We can also look at anycontinuous section of a stringusing a colon operator>>>'Monty Python'>>> print(s[0:4])The second number is oneMontbeyond the end of the slice ->>> print (s[6:7])"up to but not including"PIf the second number is>>> print s(6:20])beyond the end of the string,Pythonit stops at the endPrint (SC: 2]) *- 2. upto ='MO' butnotincholyPrint(s [8: ]) from 8 to endof string= "thon"Print (s : ]) whole stringMonty Python"String LibraryReplaces class extall Bobs - Janesall'as w/'a'sstr.capitalize( ()str.replace(old, new[, count])str.center(width[, fillchar])str. lower()str.endswith (suffix[, start[, end]])str. rstrip([chars]) removes white space rightstr.find(sub[, start[, end]])str. 1strip ([chars]) removes leftwhitestr.strip([chars]) removes bothspacestr. upper() - trus upper case.> line = 'Please have anice day"> line. startswith ('Please')Twis Searching a StringbananaWe use the find() function to search012345for a substring within another stringfind() finds the first occurrence of the>>> fruit = 'banana'substring>>> pos = fruit.find('na')>>> print (pos)If the substring is not found, find()2returns -1>>> aa = fruit.find('z')>>> print (aa)Remember that string position starts-1at zeroParsing and2131ExtractingIFrom stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008>>> data - 'From stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008'>>> atpos = data.find('8')>>> print (atpos)21>>> sppos = data find ',atpos)>>> print (sppos)31fromto>>> host = data [atpos+1 : sppos)>>> print (host)uct.ac.za!Counting Lines in a FileCount + linesof text tintxtfhand = open ('mbox. txt')Open a file read-onlyfile.count = 0 (start count)for line in fhand:Use a for loop to read each linecount = count + 1print ('Line Count: ', count)Count the lines and print outthe number of lines Reading the *Whole* File>>> fhand = open ('mbox-short. txt')We can read the whole>>> inp = fhand. read ()file (newlines and all)>>> print (len (inp))94626into a single string>>> print (inp [ : 20])From stephen marquarclass in 0-19Searching Through a Filethis code producer a blaukline between the result.fhand=open ('mbox-short.txt' )IWe can put an if statement infor line in fhand:our for loop to only print linesif line startswith ('From: ') :that meet some criteriaprint (line)only prints lines that starts w/ From'Searching Through a File (fixed)someneed to addfhandopen ('mbox-short. txt')We can strip the whitespacefor line in fhand:this line to removefrom the right-hand side ofline - line.rstrip()the string using rstrip() fromif line.atartswith('From:') :the blank spaces.print(line)the string libraryThe newline is consideredFrom: stephen.marquard@uct.ac.zalines w/o the (In) lineFrom: louis@media.berkeley.edu"white space® and isChar at the end.From: zqian@umich.edustrippedFrom: rjlowe@iupui.eduSkipping with continue Using in to select linesfhand = open ('mbox- short ext')We can look for a stringfor line in fhand:anywhere in a line as ourline - line retrip Oif not "Suct in line :selection criteria- looking only for ever.continueprint(line)From stephen marquarditic ac 28 Sat Jan 5 09:14:16 2008set sender to aphen.narquardiuct.ac. using -tFrom: stephenAuthor: stephenza Fri Jan 4 07:02:32 2008set sender to david horwitzluct.ac. 28 using -1fnaneinput ('Enter the file name')Chandopen (fname)Prompt forcount Ofor line in fhand:Lf:File Namecount - count 1print ('There were count, subject lines in' fname)Enter the file name: mbox.txtThere were 1797 subject lines in mbox.txtEnter the file name: mbox-short.txtThere were 27 subject lines in mbox-short.txtfnameLaput ('Enter the file name: ')try:Bad Filefhand - open (Ename)except:print('Tile cannot be opened:fname)-Namesquitts program i f franequit Dcountfor line in Thand:Can't be opened w/oif line Startawith('Subject:')count - countprint ('There 'vere', subject lines in'. (name)giving us sameerror codeEnter the file name: mbox.txtThere were 1797 subject lines in mbox butEnter the file name na na boo booFile cannot be opened na na boo boo Triple quotes - used - for long comments.Strings-lendfunction