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Name: [002] Ian Ozsvald
Member: 108 months
Authored: 181 videos
Description: I am the co-founder of ShowMeDo (see http://showmedo.com/about), author of `The Screencasting Handbook <http://thescreencastinghandbook.com>`_ and the founder of the professional screencast production company `ProCasts <http://procasts.co.uk>`_: .. image:: http://procasts.co.uk/media/procasts_sma ...

Completing getNumbers with Test Driven Development [ID:252] (11/17)

in series: Python 101 - easygui and csv

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We continue using the Test-Driven Development approach to write getNumbers and the associated test function. I give you the option of completing getNumbers yourself, ahead of my showing you how to write it, as an extra exercise for you.

Created May 2007, running time 3 minutes

# Two files here

#
# 910100_csvReader.py
#
import csv
import easygui

def getFileAndPath():
    "Get fully-qualified path to the csv file"
    fileAndPath = easygui.fileopenbox(title="Select .CSV file")
    print "Using:",fileAndPath 
    return fileAndPath

def getLinesInCSVFile(fileAndPath):
    "read lines in CSV file, return a list of these lines"
    linesInCSV = []
    reader = csv.reader(open(fileAndPath, "rb"))
    for row in reader:
        linesInCSV.append(row)
    return linesInCSV

def justNumbers(listOfStrings):
    "True if the list contains just numbers represented as strings"
    # e.g. ['22.4', '23.9']
    isJustNumbers = True
    for item in listOfStrings:        
        try:
            nbr = float(item)            
        except ValueError:
            isJustNumbers = False
    return isJustNumbers

def getNumbers(listOfStrings):
    "Convert a list of strings-of-numbers to a list of numbers, e.g. ['22.4', '23.9'] -> [22.4, 23.9]"
    numbers = []
    for item in listOfStrings:
        # TODO convert item to float, add to numbers list
        pass
    return numbers

if __name__ == "__main__":
    # get the file-name
    fileAndPath = getFileAndPath()
    print fileAndPath
        
    # read the CSV file
    linesInCSV = getLinesInCSVFile(fileAndPath)
    print linesInCSV
        
    print
    print "Headings:",linesInCSV[0]
    for n in range(1,4):
        print linesInCSV[n]

#
# 910100_testCsvReader.py
#
import csvReader

def testJustNumbersOnNumbers():
    listOfStrings = ['22.4', '23.9']
    assert csvReader.justNumbers(listOfStrings)
    
def testJustNumbersOnBadNumbers():
    listOfStrings = ['abc', '23.9']
    assert csvReader.justNumbers(listOfStrings) == False

def testGetNumbers():
    listOfStrings = ['22.4', '23.9']
    assert csvReader.getNumbers(listOfStrings) == [22.4, 23.9]

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All comments excluding tick-boxed quick-comments

2:55 Suggested pause point for float() and append exercise


I cannot get my nosetests to run without errors. I copied this function from your source code and can you help. I keep getting the assertion error in DOS.

def getNumbers(listOfStrings):

"Convert a list of strings-of-numbers to a list of numbers, e.g. ['27.8', '24.3'] -> [27.8, 24.3]"

numbers = []

for item in listOfStrings:

nbr = float(item)

numbers.append(nbr)

return numbers


We say 'assert something' and if 'something' is True then execution continues, but if 'something' is False then we break with an error.

It lets us test that certain conditions are definitely True before we continue with other code.

There's more background here:

http://en.wikipedia.org/wiki/Assert

Ian.


Great video - again. Just wondering could you expand on what assert in a function does? The online Python help is not much help in this case.


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