Showing Revision 5 created 05/07/2015 by Udacity Robot.

1. Title:
   01-50 Finding Strings in Strings
2. Description:

   01-50 Finding Strings in Strings

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   So I want to introduce one more operation on strings, which
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   we'll find very useful, which is the Find operation. It gives
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   us the way in a big string to find some sub-string
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   that we're looking for. The way we use Find is a little
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   different from the way we've used other operators so far. Because
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   Find is actually a method, and what that means is it's
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   a built in procedure provided by Python. We'll be able to
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    define our own procedures soon, we'll get to that in unit two.
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    Find is a procedure that operates on strings, so we use it by having
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    a string followed by .find, followed by
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    a parentheses, then we pass in another string.
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    Which is the string that we want to find in
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    the first string. And the output of Find is the
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    position in the string where that sub-string is found, the
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    first occurrence of the string. So, if that string happens
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    to occur in more places than one in the
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    input string, the result of find is always going to give
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    us the position. That's the number where the first occurrence
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    of the sub-string occurs. So the output of using Find
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    will be the first position in the search string, which
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    is this blue string right here, where the target string,
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    which is the purple string, occurs. So that will be
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    a number. If the target string is not a found anywhere
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    in the search string, then the output would be negative
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    1. So let's try a few examples to understand how
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    that works and we'll do this in the Python interpreter.
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    Here I've initialized the variable Pythagoras to hold the string here
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    that's been attributed to Pythagoras. We don't know if
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    he really said it. But it says there's a geometry
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    in the humming of strings, there is music in
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    the spacing of spheres. So now, we have that variable
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    initialized, so I'm going to invoke Find, using Pythagoras as
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    the string that we're searching in, and that's the value
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    that we initialized it to with a string, passing in
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    as the search string the string string. When we run
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    this, we see that we get 40 as the result. If we counted, this is position 0, we
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    would see string starting at position 40. Since I
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    don't want to count that far, we can use our indexing
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    to see if that's right. So let's print Pythagoras
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    starting from index 40, we could print all the
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    way to the end using a colon. And, when
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    we run that, we see that it starts with string
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    which is what we found with the Find. We can search
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    for other positions if we search for Pythagoras the single letter T.
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    Well that matches the beginning, so we should find the resulted position
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    0 which is what we get and we can look for sphere.
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    [BLANK_AUDIO]
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    That will match sphere at the end. We get
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    position 86. Let's print the quote from position 86. And
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    we see the end of the quote starting from sphere. [SOUND]
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    If we search for a string that's not in the string
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    that we're using as the search string, so let's look for
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    say, algebra, which was not in the quote from Pythagoras, we
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    get the output negative one. That means the string was not found.