Cannot concatenate 'str' and 'float' objects?

Question

Our geometry teacher gave us an assignment asking us to create an example of when toy use geometry in real life, so I thought it would be cool to make a program that calculates how many gallons of water will be needed to fill a pool of a certain shape, and with certain dimensions.

Here is the program so far:

import easygui easygui.msgbox("This program will help determine how many gallons will be needed to fill up a pool based off of the dimensions given.") pool=easygui.buttonbox("What is the shape of the pool?",               choices=['square/rectangle','circle']) if pool=='circle': height=easygui.enterbox("How deep is the pool?") radius=easygui.enterbox("What is the distance between the edge of the pool and the center of the pool (radius)?") easygui.msgbox=("You need "+(3.14*(float(radius)**2) * float(height)) + "gallons of water to fill this pool.") 

i keep getting this error though:

easygui.msgbox=("You need "+(3.14*(float(radius)**2) * float(height))  + "gallons of water to fill this pool.") TypeError: cannot concatenate 'str' and 'float' objects 

what do i do?

Answer 1

All floats or non string data types must be casted to strings before concatenation

This should work correctly: (notice the str cast for multiplication result)

easygui.msgbox=("You need "+ str(3.14*(float(radius)**2) * float(height)) + "gallons of water to fill this pool.") 

straight from the interpreter:

>>> radius = 10 >>> height = 10 >>> msg = ("You need "+ str(3.14*(float(radius)**2) * float(height)) + "gallons of water to fill this pool.") >>> print msg You need 3140.0gallons of water to fill this pool. 

Answer 2

There is one more solution, You can use string formatting (similar to c language I guess)

This way you can control the precision as well.

radius = 24 height = 15  msg = "You need %f gallons of water to fill this pool." % (3.14 * (float(radius) ** 2) * float(height)) print(msg)  msg = "You need %8.2f gallons of water to fill this pool." % (3.14 * (float(radius) ** 2) * float(height)) print(msg) 

without precision

You need 27129.600000 gallons of water to fill this pool.

With precision 8.2

You need 27129.60 gallons of water to fill this pool.