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Python 2.7 Tutorial

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#7: Comments and Strings Expanded

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On this page: commenting with #, multi-line strings with """ """, printing multiple objects, the backslash "\" as the escape character, '\t', '\n', '\r', and '\\'.

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Video Summary

  • Most of the print statements in this script were commented out initially, which were uncommented throughout the video. This is the shell output.
  • As stated in earlier tutorials, the print function tells Python to immediately display a given string once the command is executed. To designate a string for the print function to display, surround it in either single-quotes (' ') or double-quotes (" "). Both options are available so you can still use quotes within your string if need be. Ex: print "how are you doin' today?"
  • If the pound symbol (#) is placed before a command or any sort of string of characters, the command will appear in red and Python will ignore it during code execution. This can be used within Python to provide helpful comments to those looking at your code, or to "turn off" certain lines of code in order to test for bugs.
  • Surrounding a string with triple double-quotes (""" """) allows you to have any combination of quotes and line breaks within a string and Python will still interpret it as a single entity.

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  • You can specify multiple strings with the print statement. Just separate them out with a comma ',', and they will be printed with a space in between:
    >>> print 'apple', 'orange', 'pear'
    apple orange pear 
  • In Python strings, the backslash "\" is a special character, also called the "escape" character. It is used in representing certain whitespace characters: "\t" is a tab, "\n" is a newline, and "\r" is a carriage return.
    >>> print 'apple\torange'
    apple	orange 
    >>> print 'apple\norange'
  • Conversely, prefixing a special character with "\" turns it into an ordinary character. This is called "escaping". For example, "\'" is the single quote character. 'It\'s raining' therefore is a valid string and equivalent to "It's raining". Likewise, '"' can be escaped: "\"hello\"" is a string begins and ends with the literal double quote character. Finally, "\" can be used to escape itself: "\\" is the literal backslash character.
    >>> print 'It\'s raining'
    It's raining 
    >>> 'It\'s raining'          # Same string specified differently
    "It's raining" 
    >>> print "\"hello\""
    >>> print '"\\" is the backslash'   # Try with "\" instead of "\\"
    "\" is the backslash 
  • There are tons of handy functions that are defined on strings, called string methods. Learn about the ones on substringhood and also on case manipulation in this tutorial. This part 2 tutorial covers string methods for finding where a particular substring is located, and also for testing whether or not certain condition holds for every character.
  • Once you get comfortable with lists (upcoming), you should also check out Splitting and Joining Strings.