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Section 12.10 Multiple Choice Questions

Activity 12.10.1.

11-9-1: What will the following code print? 
import re
hand = open('mbox-short.txt')
for line in hand:
    line = line.rstrip()
    if re.search('^From:', line):
        print(line)
  • Any line containing ’From’
  • The ’^’ symbol matches strings from the beginning of the line.
  • Any line that starts with ’From’
  • It must include the colon to match.
  • Any line that starts with ’From:’
  • Correct! The regex equation will match with any line beginning with ’From:’.
  • Any line containing ’From:’
  • The ’^’ symbol matches strings at the beginning of the line.

Activity 12.10.2.

11-9-2: Which of the following options is the correct way to import the regex library?
  • import regex
  • We shorten regex a little more!
  • import re
  • This is how to import the regex library.
  • import Regex
  • Try shortening regex and using all lowercase.
  • import Re
  • Close, but Python is case sensitive.

Activity 12.10.3.

11-9-3: Which of these option(s) will match digits in a string? Select all that apply.
  • [0-9]
  • This is one way to match all digits using regex.
  • \D
  • \D matches any non-digit character.
  • \d
  • \d matches any digit from 0 to 9.
  • \w
  • \w matches word characters, not digits.

Activity 12.10.4.

11-9-4: Which of these lines will be matched when the following code is run? 
import re
hand = open('mbox-short.txt')
for line in hand:
    line = line.rstrip()
    if re.search('\$.+', line):
        print(line)
  • It will cost you $1.00
  • There is a dollar sign followed by one or more characters.
  • This will match a dollar sign followed by at least one character.
  • $2.50 is your change
  • The dollar sign in this line is followed by more than one character.
  • You owe three dollars.
  • The string needs to include a dollar sign.

Activity 12.10.5.

11-9-5: True or false? The following code will match only the first email(up to the @ sign) in the string? 
import re
stri = 'From: [email protected], [email protected], [email protected]'
stri = stri.rstrip()
print(re.findall('From:.+@', stri))
  • True
  • Try again!
  • False
  • The ’+’ character in regex is greedy, therefore it will match with the entire string and not just one email.

Activity 12.10.6.

11-9-6: Which of the following options will the regular expression ^X-.*: [0-9.]+ match?
  • X-DSPAM-Probability: Accurate
  • This is missing a digit for the equation to match.
  • X-DSPAM-Confidence: 0.8475
  • This matches the given regex equation.
  • X-Wolverine-Confidence: 1
  • This line matches with the given regex equation.
  • X Wolverine-Confidence: 0.53
  • This is missing a dash between ’X’ and other letters.

Activity 12.10.7.

11-9-7: Which of the following regex statements will match and return any price of the form $3.45 or $23.32 or $400 found in the string ‘x’?
  • re.findall(’\$\d+\.\d{2}’, x)
  • This would require the "." and two digits after the period
  • re.findall(’$\d+(?:\.\d{2})?’, x)
  • The ’$’ needs to be escaped with a ’\’
  • re.findall(’\$\d+(\.\d{2})?’, x)
  • This will only return the "." and digits after if they exist
  • re.findall(’\$\d+(?:\.\d{2})?’, x)
  • This will allow for the period and ending two digits to be optional and will return the whole price

Activity 12.10.8.

11-9-8: Which of these command lines will match lines in mbox-short.txt starting with ‘UMich’?
  • # grep ’^Umich’ mbox-short.txt
  • grep is case sensitive!
  • $ grep ’^UMich’ mbox-short.txt
  • This is the proper use of the grep command-line.
  • $ grep ’UMich’ mbox-short.txt
  • This is missing a character!
  • # grep ’UMich’ mbox-short.txt
  • Not quite the correct symbol at the start of the line.

Activity 12.10.9.

11-9-9: If you are having trouble remembering what methods the regex library contains, which command can you use to find said methods?
  • help()
  • This will trigger the interactive help system, but not the methods of regex.
  • dir(regex)
  • We shorten regex to something shorter.
  • dir(re)
  • This will return a list containing all the methods of the regex library.
  • import re
  • This will import the regular expression module.
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