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“91974˙CH02˙ﬁnal” 2012/12/14 13:58 page 47 #3
2.3 More About the math Module 47
Session 2.1 shows the interactive Python environment as we evaluate each of these approx-
imations.
>>> 22/7
3.1428571428571428
>>> 355/113
3.1415929203539825
>>> import math
>>> 9801/(2206*math.sqrt(2))
3.1415927300133055
>>>
Session 2.1 Simple approximations for pi
There is one Python element that is new in Session 2.1: the statement import math. Recall
that the import statement allows us to gain access to a Python module that contains
additional functionality that we might ﬁnd useful. In this case, we need to compute the
square root of 2. After loading the math module, we can use the sqrt() function to do
this for us.
math
Module
As we mentioned earlier, there are many mathematical helper functions available in the
math module. Unfortunately, it is sometimes diﬃcult to know what they are and what
they are called. To remedy this, Python has a built-in help subsystem that allows you to
see the documentation for a particular module. To use help, simply give the command
help("modulename") where the module name is the particular module you are interested
in. For example, Session 2.2 shows the result of asking for help on the math module. You
might ﬁnd it interesting that in addition to typical math functions such as sin, log, and
pow, the math module contains two constants, e and pi.
“91974˙CH02˙ﬁnal” 2012/12/14 13:58 page 48 #4
48 CHAPTER 2
π
thon
>>> help("math")
Help on module math:
NAME
math
FILE
MODULE DOCS
http://www.python.org/doc/current/lib/module-math.html
DESCRIPTION
mathematical functions defined by the C standard.
FUNCTIONS
acos(...)
acos(x)
Return the arc cosine (measured in radians) of x.
asin(...)
asin(x)
Return the arc sine (measured in radians) of x.
.
.many more functions here...
.
sqrt(...)
sqrt(x)
Return the square root of x.
tan(...)
tan(x)
Return the tangent of x (measured in radians).
tanh(...)
tanh(x)
Return the hyperbolic tangent of x.
DATA
e = 2.7182818284590451
pi = 3.1415926535897931
>>>
Session 2.2 Asking for help on a Python module

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