CSCI 150 - Foundations of Computer Science

Fall 2013

Programming Exercises: After Test 3

Write a function called reversedList1(lst). It should create a new list with the elements of the original list in reversed order. It should iterate over list values.
```
>>> reversedList1(['a', 'b', 'c'])
['c', 'b', 'a']
```
Write a function called reversedList2(lst). It should create a new list with the elements of the original list in reversed order. It should iterate over list indices.
```
>>> reversedList2(['a', 'b', 'c'])
['c', 'b', 'a']
```
Write a function called purgeDuplicates(lst). It should create a new list with duplicated elements of the original list purged.
```
>>> purgeDuplicates([1,2,3,4,1,3,5,7])
[1, 2, 3, 4, 5, 7]
```
Write a function called longWordsOnly(s, minLength). It should create a list of words from the string s that contain at least minLength characters.
```
>>> longWordsOnly('Only words of length five or longer are to be included.', 5)
['words', 'length', 'longer', 'included.']
```

Write a function called wordsFromFile(filename). It will return a list of every uniquely appearing word in the file designated by filename. afterBreak.txt is the file used for the example below:

>>> wordsFromFile('afterBreak.txt')
['simple', 'text', 'is', 'are', 'file', 'demonstration', 'use', 'for', 'should', 'These', 'written', 'perfectly', 'This', 'couple', 'functions', 'read.', 'repeated', 'words', 'with', 'a', 'functions.', 'being', 'purposes.', 'of', 'work', 'well', 'It', 'this', 'Certain', 'repeatedly.']

Write a function called countsFromFile(filename). It will return a dictionary mapping each word in filename to the number of times it appears:

>>> countsFromFile('afterBreak.txt')
{'simple': 1, 'text': 2, 'is': 2, 'are': 1, 'file': 3, 'demonstration': 1, 'use': 1, 'for': 2, 'should': 1, 'These': 1, 'written': 1, 'perfectly': 1, 'This': 1, 'couple': 1, 'functions': 1, 'read.': 1, 'repeated': 1, 'words': 1, 'with': 2, 'a': 2, 'functions.': 1, 'being': 1, 'purposes.': 1, 'of': 1, 'work': 1, 'well': 1, 'It': 1, 'this': 1, 'Certain': 1, 'repeatedly.': 1}

Write a function called prefixes(words, filename, size) that will output to a file, one per line, each prefix of each element of the list words of length size. If the word is shorter than size, the entire word will be included.
```
>>> prefixes(['This', 'is', 'a', 'test', 'of', 'the', 'function'], 'pre.txt', 3)
>>> open('pre.txt').read()
'Thi\nis\na\ntes\nof\nthe\nfun\n'
```
Write a function called toFileInverted(d, filename) that outputs the contents of a dictionary to the specified file. Each line will contain a space-separated key-value pair, with the value first.
```
>>> toFileInverted({'Moe': 10000, 'Larry': 20000, 'Shemp': 30000}, 'stoogesPay.txt')
>>> open('stoogesPay.txt').read()
'10000 Moe\n20000 Larry\n30000 Shemp\n'
```
Write a function called series(error) that computes the sum of the infinite series of 1/2ⁿ for all non-negative n (i.e., 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + ...).
```
>>> series(0.001)
1.9990234375
>>> series(0.00000001)
1.9999999925494194
```
Write a function called names(filename). It will receive from user input a series of names. It will output to the specified file each name with a count of the number of times the name appeared.
```
>>> names('stooges.txt')
Name:Moe
Name:Larry
Name:Joe
Name:Curly
Name:Joe
Name:Shemp
Name:Larry
Name:Joe
Name:
>>> open('stooges.txt').read()
'Larry 2\nShemp 1\nMoe 1\nJoe 3\nCurly 1\n'
```