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Questions and Answers
The index of the first item in a list is 1.
False
A module behaves like a function, but has a slightly different syntax.
False
In a dictionary, a -> separates a key and its value.
False
While the median of a list of values occurs most frequently, it is not always a unique value.
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All data output to or input from a text file must be strings.
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To prevent aliasing, a new object can be created and the contents of the original can be copied to it.
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Many applications now use data mangling to protect information transmitted on networks.
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The string method isalphabetic returns True if the string contains only letters or False otherwise.
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In Python, an index is used to specify the position of an element within a list.
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The remove file system function is included in the os.path module.
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A Caesar cipher uses a plaintext character to compute one encrypted character.
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A Python dictionary's elements are referenced by their indexes.
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Strings in Python are mutable data structures.
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Using a tuple is more efficient when the data structure will not change.
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The list method ascending mutates a list by arranging its elements in ascending order.
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It is more convenient to define a function in a Python shell than in an IDLE window.
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Study Notes
Functions and Methods
- Main function in scripts often does not require arguments and typically returns no value.
- Functions and methods can both return values, they differ primarily in their association with objects.
- Methods are invoked on objects, while functions exist independently.
- Python uses the
if __name__ == "__main__":block to determine script entry points, enabling scripts to run without a dedicated init function.
Data Structures
- Lists in Python are indexed starting from 0; the first item is at index 0, not 1.
- The median refers to the middle value in a sorted list, not the most frequently occurring value.
- A dictionary uses colons (
:) to separate keys from values, not arrows (->). - The index of the last item in a list corresponds to
length - 1, not the total length.
File Handling
- When opening a file in write mode (
'w'), if the file does not exist, Python does not raise an error; it creates the file. - Files can be read and written in string format only; other datatypes must be converted to strings.
List Operations
- Elements in lists can be replaced using their index, which refers to their position, not the list itself.
- Each item in a list has a unique index.
- Lists support mutation, whereas tuples do not; this affects their performance and safety.
Tuples vs. Lists
- Tuples are immutable and therefore can use less memory, offering faster performance for fixed-size data.
- Lists are mutable, allowing modification of elements but can lead to accidental changes.
- Use tuples for data that won't change, like constants or coordinates; use lists for mutable data, like to-do lists.
Error Handling
- Using
popwith a non-existent key in a dictionary raises an error. - Python raises an error if a file opened for reading (
'r') does not exist.
Miscellaneous
- Data structures should be chosen for specific use cases, considering mutability and safety.
- The string method that checks if characters are alphabetic does not return True for non-alphabetic characters.
- The method to sort lists in ascending order is
sort(), which directly modifies the original list.
Studying That Suits You
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Description
Test your knowledge of Python functions and methods with this quiz. You will answer questions about the main function, list indexing, and the differences between functions and methods. It's a great way to reinforce your understanding of Python programming concepts.
