Python Pocket Reference, 3rd Edition

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Python Pocket Reference

A Context object in this module allows for specifying preci-

sion (number of decimal digits) and rounding modes (down,

ceiling, etc.):

>>> decimal.Decimal(1) / decimal.Decimal(7)

Decimal("0.1428571428571428571428571429")

>>> decimal.getcontext().prec = 4

>>> decimal.Decimal(1) / decimal.Decimal(7)

Decimal("0.1429")

Type Conversions

Tables 10 and 11 define common built-in tools for convert-

ing from one type to another.

Table 10. Sequence converters

Converter Converts from Converts to

list(X) map(None, X)

[n for n in X]

a

a

The list comprehension form is much slower than list(), and list() has

made this form of map(None, ...) obsolete since Version 2.2.

String, tuple, user-defined

sequence, any iterable

List

tuple(X) String, list, user-defined sequence,

any iterable

Tuple

''.join(X) Sequence of strings String

Table 11. String/object converters

Converter Converts from Converts to

eval(S) String Any object with a syntax

(expression)

int(S [, base])

a

float(S)

long(S [, base])

String or number Integer, float, long

repr(X)

str(X)

`X`

(back quotes)

Any Python object String (

repr is as code,

str is user-friendly, back

quotes yield the same as

repr)

X%Y (string formatting) Objects with format codes String