A Comprehensive Introduction to Python Programming and ... - MSDL

1.2 Language Features 5 / 75
Notes:
Sequence Description
\newline Ignored
\\ \
\’ Single quote
\" Double quote
\a ASCII Bell Character (BEL)
\b ASCII Backspace Character (BS)
\f ASCII Form Feed Character (FF)
\n ASCII Line Feed Character (LF)
\Nname Unicode character named ’name’ (Unicode only)
\r ASCII Carriage Return Character (CR)
\t ASCII Horizontal Tab Character (TAB)
\uhhhh Character with the 16-bit Hexadecimal value hhhh
(Unicode Only)
\Uhhhhhhhh Character with the 32-bit Hexadecimal value
hhhhhhhh (Unicode Only)
\v ASCII Vertical Tab Character (VT)
\ooo ASCII Character with the octal value ooo
\hh ASCII Character with the hexadecimal value hh
1. Two string adjacent string literals will be concatenated at compile time. For
example, "Hello"" world!" will be concatenated into "Hello world!". This
allows to easily break string literals across multiple lines. Comments are allowed
between the parts of the string. Also, different quotation marks can be used for
each part. The different parts of the string must be enclosed in parantheses if the
string is to span multiple lines, if it is not already the case (eg for function calls).
2. String literals can also be enclosed within three double quotes, in which case
newlines within the string are become part of it.
1.2.1.4 Imaginary Numbers
Python provides built-in support for imaginary numbers. It defines 1j to be equal
to √ −1. Imaginary numbers can be written in the form a + bj, where a and b are
integers or floats.
1.2.2 Variables
Variables are not declared in Python. Since Python is a dnamically typed language,
any variable can be assigned any value, regardless of its previous type. This also holds
for instance variables in classes. Therefore, it is a good idea to initialize all instance
variables in the constructor to make sure that memory has been allocated for them, and
in order to make sure that they can safely be used inside the class. Python used to rely
on a reference counting algorithm to free the unused variables. The newer versions of
Python (ie 2.0 beta and above) rely on a more traditional garbage collection technique.