Added two new questions about number conversions.

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Guido van Rossum 1997-03-25 18:25:20 +00:00
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@ -182,6 +182,8 @@ Here's an overview of the questions per chapter:
4.41. Q. How do I delete a file? And other file questions.
4.42. Q. How to modify urllib or httplib to support HTTP/1.1?
4.43. Q. Unexplicable syntax errors in compile() or exec.
4.44. Q. How do I convert a string to a number?
4.45. Q. How do I convert a number to a string?
5. Extending Python
5.1. Q. Can I create my own functions in C?
@ -1708,6 +1710,27 @@ compile(), exec or execfile(), it *must* end in a newline. In some
cases, when the source ends in an indented block it appears that at
least two newlines are required.
4.44. Q. How do I convert a string to a number?
A. To convert, e.g., the string '144' to the number 144, import the
module string and use the string.atoi() function. For floating point
numbers, use string.atof(); for long integers, use string.atol(). See
the library reference manual section for the string module for more
details. While you could use the built-in function eval() instead of
any of those, this is not recommended, because someone could pass you
a Python expression that might have unwanted side effects (like
reformatting your disk).
4.45. Q. How do I convert a number to a string?
A. To convert, e.g., the number 144 to the string '144', use the
built-in function repr() or the backquote notation (these are
equivalent). If you want a hexadecimal or octal representation, use
the built-in functions hex() or oct(), respectively. For fancy
formatting, use the % operator on strings, just like C printf formats,
e.g. "%04d" % 144 yields '0144' and "%.3f" % (1/3.0) yields '0.333'.
See the library reference manual for details.
5. Extending Python
===================