代写 Tweet
的分析器，练习Python编程的基础用法。
Requirement
This assignment is based on the social network company Twitter (Links to an
external site.). Twitter allows users to read and post tweets that are between
1 and 280 characters long, inclusive. In this assignment, you will be writing
functions that (we imagine) are part of the programs that manage Twitter
feeds.
Here are some example tweets:
- Standing ovation as Setsuko Thurlow is awarded a Doctor of Laws degree, honoris causa, by the University of Toronto @UofT for her tireless nuclear disarmament work and contributions to the Treaty on the Prohibition of Nuclear Weapons with @nuclearban ICAN
- Congratulations to our class of 2019 #UofTGrad19
- #UofT’s @ProbabilityProf @UofTStatSci created a mathematical model at the start of the playoffs to figure out the team’s odds of winning. He predicts their home-court advantage will give them an edge. http://bit.ly/ProbProf
Some terminology
- tweet: A message posted on Twitter. For our purposes, the message text is between 1 and
MAX_TWEET_LENGTHcharacters long (inclusive).MAX_TWEET_LENGTHis a constant. - tweet word: A word in a tweet. For our purposes, a tweet word contains only alphanumeric characters and underscores. For example,
pink_elephantis a tweet word, whilebits&piecesis not (In fact,bits&piecesis two tweet words,bitsandpieces, with an ampersand (&) between them.) - hashtag: A word in a tweet that begins with the hash symbol. Twitter uses the number sign (
#) as the hash symbol. For our assignment, we’ll use the constantHASHTAG_SYMBOLto represent the hash symbol. Hashtags are used to label important words or terms in a tweet. A valid hashtag has the hash symbol as its first character and the rest of the characters form a tweet word. In other words, a hashtag begins with the hash symbol, and contains all alphanumeric characters and underscores up to (but not including) the first non-alphanumeric character (such as space, punctuation, etc.) or the end of the tweet. A hashtag either begins a tweet or is preceded by a character that is not alphanumeric and is not an underscore. A hashtag must contain at least one alphanumeric character.#UofT,#csc108, and#Go_Raptorsare three examples of hashtags on Twitter.
Note that a hashtag is not a tweet word, because it has the hash symbol as its
first character. - mention: A word in a tweet that begins with the mention symbol. Twitter uses the at-sign (
@) as the mention symbol. For our assignment, we’ll use the constantMENTION_SYMBOLto represent the mention symbol. Mentions are used to direct a message at or about a particular Twitter user, so the word should be a Twitter username (but for the purposes of this assignment, we will not check if the username is valid we’ll just assume it). For our purposes, the definition of a mention is very similar to that of a hashtag. A valid mention has the mention symbol as its first character and the rest of the characters form a tweet word. In other words, a mention begins with the at-sign, and contains all alphanumeric characters and underscores up to (but not including) the first non-alphanumeric character (such as space, punctuation, etc.) or the end of the tweet. A mention either begins a tweet or is preceded by a character that is not alphanumeric and is not an underscore. A mention must contain at least one alphanumeric character.@redcrosscanada,@UN_Women, and@UofTGrad2019are three examples of Twitter mentions.
Note that a mention is not a tweet word, because it has the mention symbol as
its first character.
Here are some more interesting examples of how we will treat tweet words,
hashtags, and mentions in this assignment.
In the tweet
Raptors win championship,#NBAFINALS, Go @Raptors!!! #WeTheNorth
we have four tweet words (Raptors,win,championship, andGo), two hashtags (#NBAFINALSand#WeTheNorth), and one mention (@Raptors). It is important to note that in this example there is no space
between the first comma and the hashtag#NBAFINALS, there is a comma
immediately following the hashtag#NBAFINALS, there are three exclamation
marks immediately following the mention@Raptors, and there are more than
one space after the exclamation marks. All these are valid in a tweet. Also
note that the first occurrence of the wordRaptorsis not considered to be
a mention, because it does not have the mention symbol.
In the tweet
@UofT welcomes its 2019 graduates! #UofTGrad2019#graduation!
we have four tweet words (welcomes,its,2019, andgraduates), two hashtags (#UofTGrad2019and#graduation), and one mention (@UofT). It is important to note that in this example there is no space
between hashtags#UofTGrad2019and#graduation. This is also valid in
a tweet.
Some more obscure yet valid examples: - In
something#something_elsewe considersomethingis a tweet word and#something_elseis a hashtag. - In
no@spaces#whatsoever?!we considernois a tweet word,@spacesis a mention, and#whatsoeveris a hashtag.
For a complete list of Twitter terms, check out the Twitter glossary (Links to
an external site.).
Starter code
For this assignment, we are giving you some files, including a Python starter
code files. Please download the Assignment 1 Files and extract the zip
archive.
- Starter code: tweet.py
This file contains some constants, the header and the complete docstring (but
not body) for the first function you are to write. Your job is to complete
this file. - Checker: a1_checker.py
We have provided a checker program that you should use to check your code. See
below for more information about a1_checker.py.
Constants
Constants are special variables whose values do not change once assigned. A
different naming convention (uppercase pothole) is used for constants, so that
programmers know to not change their values. For example, in the starter code,
the constant MAX_TWEET_LENGTH is assigned the value 50 at the beginning of
the module and the value of MAX_TWEET_LENGTH should never change in your
code. When writing your code, if you need to use the value of the maximum
tweet length, you should use MAX_TWEET_LENGTH . The same goes for the
other constant values.
Using constants simplifies code modifications and improves readability. If we
later decide to use a different tweet length, we would only have to change the
length in one place (the MAX_TWEET_LENGTH assignment statement), rather
than throughout the program.
What to do
In the starter code file tweet.py , complete the following function
definitions. Use the Function Design Recipe that you have been learning in
this course. We have included the type contracts in the following table;
please read through the table to understand how the functions will be used.
We will be evaluating your docstrings in addition to your code. Please include
two examples in your docstrings. You will need to paraphrase the full
descriptions of the functions to get an appropriate docstring description.
Function name: (Parameter types) -> Return type | Full Description
(paraphrase to get a proper docstring description)
—|—
is_valid_tweet: (str) -> bool | The parameter represents a potential tweet.
The function should return True if and only if the tweet contains between
1 and MAX_TWEET_LENGTH characters, inclusive.
compare_tweet_lengths: (str, str) -> int | The two parameters represent
valid tweets. This function must return one of three integers: 1 (if the
first tweet is longer than the second), -1 (if the second tweet is longer
than the first), or 0 (if the tweets have the same length).
add_hashtag: (str, str) -> str | The first parameter represents a valid
tweet. The second parameter represents a tweet word. Appending a space, a hash
symbol, and the tweet word to the end of the original tweet will result in a
potential tweet. If the potential tweet is a valid tweet, the function should
return the potential tweet. If the potential tweet is not a valid tweet, the
function should return the original tweet. For example (assuming the hash
symbol is '#' ), if the first argument is 'I like' and the second
argument is 'csc108' , then the function should return 'I like #csc108' , if MAX_TWEET_LENGTH is at least 14. Otherwise, it should return 'I like' .
contains_hashtag: (str, str) -> bool | The first parameter represents a
valid tweet, and the second parameter represents a tweet word. This function
should return True if and only if the tweet contains a hashtag made up of
the hash symbol and the tweet word. For example (assuming the hash symbol is '#' ), if the first argument is 'I like #csc108' , and the second
argument is 'csc108' , then the function should return True . Notes:
If the first argument is 'I like #csc108' , and the second argument is 'csc' , then the function should return False. Also, if the first argument
is 'I like #csc108, #mat137, and #phl101' , and the second argument is csc108 , the function should return True . Hint: Use the helper function
clean that is provided in the starter code.
is_mentioned: (str, str) -> bool | The first parameter represents a valid
tweet, and the second parameter represents a tweet word. This function should
return True if and only if the tweet contains a mention made up of the
mention symbol and the tweet word. For example (assuming the mention symbol is'@' ), if the first argument is 'Go @Raptors!' , and the second
argument is 'Raptors' , then the function should return True . Hint:
This function is very similar to the function contains_hashtag . What can
you do to avoid writing the same code twice?
add_mention_exclusive: (str, str) -> str | The first parameter represents a
valid tweet and the second parameter represents a tweet word. Appending a
space, a mention symbol, and the tweet word to the end of the original tweet
will result in a potential tweet. If the potential tweet is valid, the
original tweet contains the given tweet word, and the original tweet does not
mention the given tweet word, the function should return the potential tweet.
Otherwise, the function should return the original tweet. For example
(assuming the mention symbol is '@' ), if the first argument is 'Go Raptors!' and the second argument is 'Raptors' , then the function
should return 'Go Raptors! @Raptors' . If, on the other hand, the first
argument is 'Go @Raptors!' and the second argument is 'Raptors' , then
the function should return the original tweet 'Go @Raptors!' . Hint: can
you use one of your other functions as a helper function?
num_tweets_required: (str) -> int | The parameter represents a message. This
function should return the minimum number of tweets that would be required to
communicate the entire message. Recall the maximum length of a tweet is MAX_TWEET_LENGTH . Hint: the ceil function in the math module is
useful here.
get_nth_tweet: (str, int) -> str | The first parameter represents a message
that a Twitter user would like to post, and the second parameter, n ,
represents an integer greater than or equal to 0. If the message contains too
many characters, it would need to be split up into a sequence of tweets. All
of the tweets in the sequence, except possibly the last tweet, would be of
length MAX_TWEET_LENGTH . This function should return the nth valid tweet
in the sequence of tweets. Note that the first tweet in the sequence has index
0 (the 0th tweet), the second tweet in the sequence has index 1, and so on. If
the value of the second parameter is too large, so there is no index- n
tweet in the sequence, this function should return an empty string.
Using Constants
As we discuss in section Constants above, your code should make use of the
provided constants. If the value of one of those constants were changed, and
your program rerun, your functions should work with those new values.
For example, if MAX_TWEET_LENGTH were changed, then your functions should
work according to the new maximum tweet length.
Your docstring examples should reflect the given values of the constants in
the provided starter code, and do not need to change.
No Input or Output
Your tweet.py file should contain the starter code, plus the function
definitions specified above. tweet.py must not include any calls to the print and input functions. Do not add any import statements. Also,
do not include any function calls or other code outside of the function
definitions.
How should you test whether your code works
First, run the checker and review ALL output you may need to scroll. You
should also test each function individually by writing code to verify your
functions in the Python shell. For example, after defining function compare_tweet_lengths , you might call it from the shell (e.g., compare_tweet_lengths('I love', 'programming') ) to check whether it returns
the right value ( -1 ). One call usually isn’t enough to thoroughly test
the function for example, we should also test compare_tweet_lengths('programming', 'is fun') where it should return 1
and compare_tweet_lengths('this course', 'is for me!!') where it should
return 0.
