Solutions for Part B: Strings, ..., File I/O exercises

1. Accessing and Storing Web Files

# GetGA.py
#
import urllib

FileURL = 'http://csc.ucdavis.edu/~chaos/courses/clab/Homework/GettysburgAddress.txt'

file = open('ga.txt','w')

for line in urllib.urlopen(FileURL):
	file.write(line)

file.close()

2. Counting lines and words in a file

# WordLineCounts.py
#
lines = 0
words = 0
f = open('ga.txt')
for line in f:
    lines = lines + 1
    words = words + len(line.split())

f.close()
print lines, " lines, ", words, " words."

3. Counting vowels in a file

# VowelCounts.py
#
nLines = 0
nAs = 0
nEs = 0
nIs = 0
nOs = 0
nUs = 0
f = open('ga.txt')
for line in f:
    nLines = nLines + 1
    for letter in line:
        if letter == 'a':
            nAs = nAs + 1
        elif letter == 'e':
            nEs = nEs + 1
        elif letter == 'i':
            nIs = nIs + 1
        elif letter == 'o':
            nOs = nOs + 1
        elif letter == 'u':
            nUs = nUs + 1

print "File has:"
print nAs, " As"
print nEs, " Es"
print nIs, " Is"
print nOs, " Os"
print nUs, " Us"

4. Sort lines in a file

# SortFile.py
#
InputFileName = 'ga.txt'
Lines = []
f = open(InputFileName)
for line in f:
    Lines.append(line)

f.close()

Lines.sort()
SortedFileName = 'ga_sorted.txt'

file = open(SortedFileName, 'w')
for line in Lines:
    file.write(line)

file.close()

5. Iterate a one-dimensional map, storing results in a file

# OneDMapIterate.py
#
OutputFileName = "onedmap.txt"
nIterations = 20
x = 0.3
r = 4.0

file = open(OutputFileName, 'w')

for i in range(nIterations):
    x = r * x * (1.0 - x)
    line = str(i) + ' ' + str(x) + '\n'
    file.write(line)

file.close()

In [35]: cat onedmap.txt
0 0.84
1 0.5376
2 0.99434496
3 0.0224922420904
4 0.0879453645446
5 0.320843909599
6 0.871612381089
7 0.447616952887
8 0.989024065501
9 0.0434218534453
10 0.166145584355
11 0.554164916617
12 0.988264647232
13 0.0463905370552
14 0.176953820508
15 0.582564663661
16 0.972732305258
17 0.106096670262
18 0.379360667285
19 0.941784605609

6. Analyze a chaotic one-dimensional map

# OneDMapAnalyze.py
#
MeanValue = 0.0
nIterates = 0

f = open('onedmap.txt')
for line in f:
    n, x = line.split()
    MeanValue = MeanValue + float(x)
	nIterates = nIterates + 1

f.close()
print "Average value = ",MeanValue/float(nIterates)