Python simple for loop issue

Question

Currently learning python. Normally a C++ guy.

if wallpaper == "Y":
    charge = (70)
    print ("You would be charged £70")
    wallpaperList.append(charge)

elif wallpaper == "N" :
    charge = (0)

else:
    wallPaper ()

surfaceArea
    totalPapers = 0
    for item in range (len(wallpaperList)):
        totalPapers += wallpaperList[item]

I am trying do a for loop for the if statement.

In c++ this will just be a simple

for (I=0; i<pRooms; i++){
}

I am trying to add the above code in a for loop but I seem to fail.

Thanks

Not sure over what you're looping... if it's pRooms, you do for i in xrange(pRooms): — erip
– erip, Commented Apr 22, 2016 at 19:30
Please correct your indentation, also, currently there are mistakes, and in Python, indentation matters. — heltonbiker
– heltonbiker, Commented Apr 22, 2016 at 19:31

erip · Accepted Answer · 2016-04-22 19:44:16Z

4

Python loops iterate over everything in the iterable:

for item in wallpaperList:
        totalPapers += item

In modern C++, this is analogous to:

std::vector<unsigned int> wallpaperList;

// ...

for(auto item: wallpaperList) {
    totalPapers += item
}

You could also just use the sum function:

cost = sum(wallpaperList)

If the charge is 70 every time, why not just do multiplication?

while wallPaper == 'Y':
    # ...

    # Another satisfied customer!
    i += 1

cost = i * 70

edited Apr 22, 2016 at 19:44

answered Apr 22, 2016 at 19:31

erip

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Comments

alexis · Accepted Answer · 2016-04-23 21:55:31Z

2

For the exact equivalent of your for loop, use range:

for (i=0; i<pRooms; i++){   # C, C++
}

for i in range(pRooms):     # Python
    ...

Both loops iterate over the values 0 to pRooms-1. But python gives you other options. You can iterate over the elements of the list without using an index:

for room in listOfRooms:
    if room.wallpaper == "Y":
        ...

List comprehensions are also nice. If you don't care about the print calls in your code, you could compute the cost in one line with something like this:

totalPapers = sum(70 for room in listOfRooms if room.wallpaper == "Y")

edited Apr 23, 2016 at 21:55

answered Apr 22, 2016 at 21:04

alexis

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