Quiz 7: Files, Exceptions, List Comprehensions, Sorting

Learning Goals

Students should be able to:

For files:

• Open files in different modes using Python's open function
• Close files in using Python's close function
• Use Python's with ... as syntax for opening and closing files.
• Read data from files by using a for loop to iterate over a file (the preferred method, which iteraties over the lines of the file), but also by using the .read, .readlines and .readline methods (where appropriate).
• Write data to files using the .write method
• Explain the difference between reading, writing, and appending files
• Understand how programs create and modify files
• Remove leading and trailing whitespace from a string (including newlines) using the .strip method.
• Split a string into lists of strings using the .split method

For exceptions

• Explain the behavior of code that uses try/except to handle exceptions.
• Write code that uses try/except to implement specified exception handling behavior.

For list comprehensions:

• Translate between for loops and list comprehensions
• Use list comprehension expressions to concisely create lists using the mapping and/or filtering patterns.

For sorting

• Understand the difference between sorted and .sort when reading and writing code involving sorting.
• Understand how strings and (possibly nested) tuples are sorted by sorted and .sort, both in ascending order (the default, when implicitly reverse=False) and in descending order (when reverse=True)
• Understand how the key keyword parameter of both sorted and .sort can be used in conjunction with a function (specified either by a helper function or by a lambda expression) to change the default order in which the values in a sequence of are sorted.
• Use the above knowledge to read and write code involving sorting.

Study Guide

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Answer Key

Solutions

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