CS50 Library for Python¶

Installation¶

Ubuntu¶

$ sudo pip3 install cs50

Fedora¶

$ sudo pip3 install cs50

Usage¶

Note

To use these functions, make sure to include import cs50 atop your file.

cs50.get_float(prompt)¶

Parameters: prompt – the str with which to prompt the user for input
Returns: the float equivalent to the line read from stdin as precisely as possible, or None on error

Prompts user for a line of text from standard input and returns the equivalent float; if text does not represent a floating-point value or would cause overflow or underflow, user is reprompted.

Example usage:

f = get_float("Enter a floating-point number: ")

cs50.get_int(prompt)¶

Parameters: prompt – the str with which to prompt the user for input
Returns: the int equivalent to the line read from stdin, or None on error

Prompts user for a line of text from standard input and returns the equivalent int; if text does not represent an integer, user is reprompted.

Example usage:

f = get_int("Enter an integer: ")

cs50.get_string(prompt)¶

Parameters: prompt – the str with which to prompt the user for input
Returns: the read line as a string sans line endings, or None on EOF.

Prompts user for a line of text from standard input and returns it as a str, sans trailing line ending. Supports CR (\r), LF (\n), and CRLF (\r\n) as line endings.

Example usage:

s = get_string("Enter a string: ")

cs50.SQL(url)¶

Parameters: url – a str that indicates database dialect and connection arguments
Returns: a cs50.SQL object that represents a connection to a database

Example usage:

db = cs50.SQL("sqlite:///foo.db")  # For SQLite, foo.db must exist
db = cs50.SQL("mysql://username:password@host:port/database")  # For MySQL
db = cs50.SQL("postgres://username:password@host:port/database")  # For PostgreSQL

cs50.SQL.execute(sql, *args, **kwargs)¶

Parameters

sql – a str that represents a single SQL statement, possibly with placeholders, with or without a trailing semicolon
*args – zero or more positional arguments with which any placeholders should be substituted
**kwargs – zero or more named arguments with which any placeholders should be substituted

Returns

for SELECTs, a list of dict objects, each of which represents a row in the result set; for INSERTs, the primary key of a newly inserted row (or None if none); for UPDATEs, the number of rows updated; for DELETEs, the number of rows deleted; for CREATEs, True on success; on error, a RuntimeError is raised

Example usage:

db = cs50.SQL("sqlite:///file.db")

db.execute("SELECT * FROM foo")

rows = db.execute("SELECT * FROM foo WHERE bar = ? AND baz = ?", 1, 2)
rows = db.execute("SELECT * FROM foo WHERE bar IN (?) AND baz IN (?)", [1, 2], [3, 4])

rows = db.execute("SELECT * FROM foo WHERE bar = :bar AND baz = :baz", bar=1, baz=2)
rows = db.execute("SELECT * FROM foo WHERE bar = :bar AND baz = :baz", {"bar": 1, "baz": 2})
rows = db.execute("SELECT * FROM foo WHERE bar IN (:bar) AND baz IN (:baz)", bar=[1, 2], baz=[3, 4])

db.execute("INSERT INTO foo (bar, baz) VALUES(?, ?)", 1, 2)
db.execute("INSERT INTO foo (bar, baz) VALUES(:bar, :baz)", bar=1, baz=2)
db.execute("INSERT INTO foo (bar, baz) VALUES(:bar, :baz)", {"bar": 1, "baz": 2})

db.execute("UPDATE foo SET bar = ?, baz = ?", 1, 2)
db.execute("UPDATE foo SET bar = :bar, baz = :baz", bar=1, baz=2)
db.execute("UPDATE foo SET bar = :bar, baz = :baz", {"bar": 1, "baz": 2})

db.execute("DELETE FROM foo WHERE bar = ? AND baz = ?", 1, 2)
db.execute("DELETE FROM foo WHERE bar = :bar AND baz = :baz", bar=1, baz=2)
db.execute("DELETE FROM foo WHERE bar = :bar AND baz = :baz", {"bar": 1, "baz": 2})