Introduction to Python
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In-Class Exercises, Session 3
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PLEASE REFER to pythonreference.com for syntax to follow in coding these Exercises |
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NOTE THAT the data files read from these exercises is located in the "parent" directory. Thus any filename in these exercises should be preceded with ../. (If you create a script in the same directory as the data file, this would not be necessary.) |
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STRINGS |
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| Ex. 3.1 | .rstrip() a string of a charactrer or whitespace. Strip the sentence of the period; strip the csv line of the newline character. Print each. |
sentence = 'Hello there treasured Python friends.'
csv_line = 'California,31,39.51,3200\n'
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Expected Output:
Hello there treasured Python friends' California,31,39.51,3200 |
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| Ex. 3.2 | .split() a string on a character or on whitespace. Split the sentence into words; split the CSV line into fields. Print each. |
sentence = 'Hello there treasured Python friends'
csv_line = 'California,31,39.51,3200'
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Expected Output:
['Hello', 'there', 'treasured', 'Python', 'friends.'] ['California', '31', '39.51', '3200'] |
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| Ex. 3.3 | Slice a string. Slice the 4-digit year, 2-digit month and 2-digit day of 'fw_line'. |
fw_line = 'DATE20150903'
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| Ex. 3.4 | Use variables to slice the 4-digit year of 'fw_line'. |
fw_line = 'DATE20150903'
start_index = 4
end_index = 8
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LISTS |
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| Ex. 3.5 | List operations. |
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Perform the noted operations on list 'x' |
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x = ['hello', 'there', 'Python', 'friends']
# print the type of the list (use type())
# show the length of the list (use len())
# access and print the first item of the list (use list subscript)
# access and print the last item of the list (use negative subscript)
# use a variable index to print the last item
last_idx = -1
print()
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Expected Output:
<class 'list'> hello friends 4 |
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LAB 1 |
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| Ex. 3.6 | Print item from a delimited string. |
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Select and print the 3rd value. Do not use a slice. |
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delimited = 'New York,31,39.51,3200'
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Expected Output:
39.51 |
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| Ex. 3.7 | Select number from a delimited string, use as number. |
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Select the 2nd value, then double it to 62. Do not use a slice. |
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delimited = 'New York,31,39.51,3200'
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Expected Output:
62 |
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| Ex. 3.8 | Print a word from a space-delimited string. |
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Print the 4th word from dickens. Then print the last word with the trailing period stripped. |
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dickens = 'It was the best of times, it was the worst of times.'
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Expected Output:
best times |
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| Ex. 3.9 | Determine number of words in a string. |
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In just two additional statements (not including printing), show the number of words in the string. |
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swanns_way = 'For a long time I used to go to bed early.'
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Expected Output:
11 |
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| Ex. 3.10 | Show selected words from a string. |
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Print the 1st word in the setence, the 5th word in the sentence, and the last word in the sentence. |
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gatsby = "In my younger and more vulnerable years my father gave me some advice..."
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Expected Output:
In more advice... |
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| Ex. 3.11 | Slice part of a string. |
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Print the numeric SKU value (the 9 digits after SKU only, not the 8) from serial. |
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serial = '#SKU000095327MRCOFFEE8CUPCAPUC'
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Expected Output:
000095327 |
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LOOPING |
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| Ex. 3.12 | Loop through and print each individual item in the list (use 'for') |
x = ['What', 'do', 'you', 'think?']
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Expected Output:
What do you think? |
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| Ex. 3.13 | List iteration and summary. |
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Use 'for' to loop through list 'xval' and count the number of iterations, then extend it to also sum up the values. Print the sum and the count. |
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xval = [3.9, 0.3, 2.1, 0.03]
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Expected Output:
4 6.33 |
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FILES |
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| Ex. 3.14 | File operations. |
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Perform the below operations: |
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filename = '../pyku.txt'
# open file 'pyku.txt' and assign to variable 'fh' (use open())
# print the type of variable 'fh'
print()
# iterate over the variable 'fh' with 'for' and print each line in the file
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Expected Output:
<class '_io.TextIOWrapper'> We're out of gouda. This parrot has ceased to be. Spam, spam, spam, spam, spam. |
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| Ex. 3.15 | Using 'with' context to open files. |
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Again open pyku.txt for reading, and loop through and print each line, but use a 'with' block to open the file. |
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filename = '../pyku.txt'
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Expected Output:
We're out of gouda. This parrot has ceased to be. Spam, spam, spam, spam, spam. |
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LAB 2 |
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| Ex. 3.16 | Loop through a list. Loop through and print each individual item in the list (use 'for') |
mylist = ['a', 'b', 'c', 'd']
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Expected Output:
a b c d |
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| Ex. 3.17 | Loop through a file and print each line. |
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Loop through the file pyku.txt and print each line as you go. You should see a blank line between each printed line (this is the newline character). |
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filename = '../pyku.txt'
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Expected Output:
We're all out of gouda. This parrot has ceased to be. Spam, spam, spam, spam, spam. |
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| Ex. 3.18 | Loop through a file and strip each line. |
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Loop through the file pyku.txt and strip and print each line as you go. You should see the lines printed without a blank line in between. |
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filename = '../pyku.txt'
fh = open(filename)
for line in fh:
# your code here
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Expected Output:
We're all out of gouda. This parrot has ceased to be. Spam, spam, spam, spam, spam. |
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| Ex. 3.19 | Loop through file and count. |
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Loop through the file pyku.txt and keep a running count of each line. Print the count at the end. |
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filename = '../pyku.txt'
fh = open(filename)
for line in fh:
# your code here
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Expected Output:
3 |
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| Ex. 3.20 | Loop through file and print one field. |
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Loop through datafile.csv and print just the first field from each line. |
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filename = '../datafile.csv'
fh = open(filename)
for line in fh:
# your code here
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Expected Output:
Alpha Beta Gamma Delta Epsilon |
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| Ex. 3.21 | Loop through file and print one slice. |
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Print the month and day from each line in FF_tiny.txt |
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filename = '../FF_tiny.txt'
fh = open(filename)
for line in fh:
# your code here
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Expected Output:
0701 0702 0103 0104 0201 0202 0103 0104 0105 |
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| Ex. 3.22 | Loop through file, isolate and double numeric value. |
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Looping through datafile.csv, isolate the int value (4th field) and double it, printing each doubled value as you loop. |
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fname = '../datafile.csv'
fh = open(fname)
for line in fh:
# your code here
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Expected Output:
6 2 0 8 4 |
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| Ex. 3.23 | Loop through file, isolate values and add together. |
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Looping through datafile.csv, isolate the int value and float value (4th and 5th fields) and add them together, printing each summed value as you loop. |
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name = '../datafile.csv'
fh = open(name)
for line in fh:
# your code here
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Expected Output:
6.3 2.1 2.2 4.8 3.6 |
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| Ex. 3.24 | Loop through file and sum up values in column. |
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Looping through datafile.csv, sum up the last column of float values. Print the sum at the end. |
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fname = '../datafile.csv'
fh = open(fname)
for line in fh:
line = line.rstrip()
# your code here
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Expected Output:
9.0 |
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Note that if you see a very long (and tiny) remainder, to use the round() function to round to one decimal place. |
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| Ex. 3.25 | Loop through file and selectively print using split(). |
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Looping through revenue.csv, print the company names for rows with 'NY' as the state. |
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filename = '../revenue.csv'
fh = open(filename)
for line in fh:
# your code here
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Expected Output:
Hipster's Dothraki Fashions The Clothiers |
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| Ex. 3.26 | Loop through file and selectively print using a slice. |
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Looping through FF_tiny.txt, print the last float value on each line for the year 1927. |
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filename = '../FF_tiny.txt'
fh = open(filename)
for line in fh:
# your code here
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Expected Output:
0.015 0.011 0.022 0.018 |
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| Ex. 3.27 | Loop through file and sum up selected value. |
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Looping through revenue.csv, sum up the float value (3rd field) only for those rows from NJ (2nd field). |
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fname = '../revenue.csv'
fh = open(fname)
for line in fh:
line = line.rstrip()
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Expected Output:
265.4 |
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SUMMARY ALGORITHM; BUILDING FROM FILE |
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| Ex. 3.28 | File line iteration and summary. |
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Use 'for' to loop through file 'revenue.csv' and count the number of iterations, then perform the operations noted below: test each step as you proceed. |
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filename = '../revenue.csv'
fh = open(filename)
counter = 0
summer = 0.0
# 1. loop through file line-by-line; strip and print each line
# 2. count each iteration; print count at end
# 3. split each line on a comma; print each split line
# 4. subscript float value from split list; print each subscripted value
# 5. convert float value (a string) to float
# 6. sum up float values; print sum after loop ends
# 7. adding a horizontal bar to separate iterations
print('------------------------------')
# close file
# print sum and count
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Expected Output:
Haddad's,PA,239.50 ["Haddad's", 'PA', '239.50\n'] 239.50 ------------------------------ Westfield,NJ,53.90 ['Westfield', 'NJ', '53.90\n'] 53.90 ------------------------------ The Store,NJ,211.50 ['The Store', 'NJ', '211.50\n'] 211.50 ------------------------------ Hipster's,NY,11.98 ["Hipster's", 'NY', '11.98\n'] 11.98 ------------------------------ Dothraki Fashions,NY,5.98 ['Dothraki Fashions', 'NY', '5.98\n'] 5.98 ------------------------------ Awful's,PA,23.95 ["Awful's", 'PA', '23.95\n'] 23.95 ------------------------------ The Clothiers,NY,115.20 ['The Clothiers', 'NY', '115.20\n'] 115.20 ------------------------------ 7 662.0100000000001 |
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