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Laboratory 5: Lists, Files, Exceptions, Strings
Prerequisits: +exceptions, +string handling
Provide the following functionality in a file training5.py:
Write a function count_sub_in_file(filename,s) that takes two
arguments: the substring s (of type string) and a filename
(of type string). The function should return the number of
occurrences of s in the file given through filename. (Note that
each string object has a method count that should be used
here.)
You can test your function count_sub_in_file on Alice's
Adventures in Wonderland which you can download from
http://www.gutenberg.org/files/28885/28885-8.txt
- How often does the substring "Alice" occur? Expect several hundred.
- How often does the substring "alice" occur? Expect a very small number.
(On Mac OS X and Linux, you
can use the
wget http://www.gutenberg.org/files/28885/28885-8.txt command from a
shell to download the file. Otherwise use your browser and save the file in the same directory as your training5.py file.)
Modify the function count_sub_in_file(filename, s) so that if
the file with name filename cannot be opened, the value -1 is
returned (instead of the number of substrings s).
Write a function count_vowels(s) that returns the number of
letters 'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U' in a given string
s (the return value is of type integer).
Examples:
In [ ]: count_vowels('This is a test')
Out[ ]: 4
In [ ]: count_vowels('aoeui')
Out[ ]: 5
In [ ]: count_vowels('aoeuiAOEUI')
Out[ ]: 10
In [ ]: count_vowels('N0 v0w3ls @t @ll ln thls strlng')
Out[ ]: 0
Provide the following functionality in a file lab5.py:
Write a function vector_product3(a, b) that takes two sequences
of numbers. Both sequence a and sequence b have three
elements. With inputs a=[ax, ay, az] and b=[bx, by, bz], the
function should return a list which contains the vector product of
3d-vectors a and b, i.e. the return value is the list:
[ay * bz - az * by, az * bx - ax * bz, ax * by - ay * bx].
Examples:
In [ ]: vector_product3([1, 0, 0], [0, 1, 0])
Out[ ]: [0, 0, 1]
In [ ]: vector_product3([1, 2, 4], [3, 5, 6])
Out[ ]: [-8, 6, -1]
Write a function seq_mult_scalar(a,s) which takes a list of numbers a and a scalar (i.e. a number) s. For the input a=[a0, a1, a2,.., an] the function should return [s * a0, s * a1, s * a2, ..., s * an].
Example:
In [ ]: seq_mult_scalar([-4, 9, 1], 10)
Out[ ]: [-40, 90, 10]
A function powers(n,k) that returns the list [1,n,n^2,n^3,...,n^k] where k is an integer. Note that there should be k+1 elements in the list.
Example:
In [ ]: powers(2, 3)
Out[ ]: [1, 2, 4, 8]
In [ ]: powers(0.5, 2)
Out[ ]: [1.0, 0.5, 0.25]
A function traffic_light(load) that takes a floating point number load. The function should return the string:
- "green" for values of load below 0.7.
- "amber" for values of load equal to or greater than 0.7 but smaller than 0.9
- "red" for values of load equal to 0.9 or greater than 0.9
Example:
In [ ]: traffic_light(0.5)
Out[ ]: 'green'
The submission of lab5.py is assessed.
Last updated: 2016-10-30 at 12:17
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