Intro to operations on strings

Loosely Based on Lecture Materials By: Milad Fatenejad, Katy Huff, Joshua R. Smith, Tommy Guy, Will Trimble, and Many More

There are operations that can be done with strings.



In [21]:

    
firstName = "Johan"



In [22]:

    
lastName = "Gambolputty"

When concatenating strings, we must explicitly use the concatenation operator +. Computers don't understand context.



In [23]:

    
fullName = firstName + lastName



In [24]:

    
print fullName









    



JohanGambolputty



In [25]:

    
fullName = firstName + " " + lastName



In [26]:

    
print fullName









    



Johan Gambolputty

You can also think of strings as a sequence of smaller strings or characters. We can access a piece of that sequence using []. Gotcha - Python (and many other langauges) start counting from 0.



In [27]:

    
fullName[0]









    Out[27]:





'J'



In [28]:

    
fullName[4]









    Out[28]:





'n'

One more gotcha - in Python, if you want a range (or "slice") of a sequence, you get everything before the second index:



In [29]:

    
fullName[0:4]









    Out[29]:





'Joha'



In [30]:

    
fullName[0:5]









    Out[30]:





'Johan'

You can see some of the logic for this when we consider implicit indices



In [31]:

    
fullName[:5]









    Out[31]:





'Johan'



In [32]:

    
fullName[5:]









    Out[32]:





' Gambolputty'

There are other operations defined on string data. IPython lets you do tab-completion after a dot ('.') to see what an object (i.e., a defined variable) has to offer. Try it now!



In [ ]:

    
str.

Let's look at the upper method. What does it do? Lets take a look at the documentation. IPython lets us do this with a question mark ('?') before or after an object (again, a defined variable).



In [1]:

    
str.upper?

So we can use it to upper-caseify a string.



In [ ]:

    
fullName.upper()

You have to use the parenthesis at the end because upper is a method of the string class.

For what its worth, you don't need to have a variable to use the upper() method, you could use it on the string itself.



In [ ]:

    
"Johann Gambolputty".upper()

What do you think should happen when you take upper of an int? What about a string representation of an int?



In [ ]: