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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 =================== |