1. Introducing Python CS 4320, SPRING 2015

2. Format: Field widths and Alignment The string representation of a value can be padded out to a specific width with spaces This will make neat columns of data when printed The desired number of characters is specified by including a colon in the replacement field, right after the parameter index if it is included: {2:10} or {:10} ◦Following the colon is the number of total characters the value is to take If the value takes more than the specified number of characters when first converted, no padding is done ◦This will cause columns to not align properly, but no data is lost An alignment character can appear between the colon and the width ◦< forces left alignment {2:<10} ◦> forces right alignment {2:>10} ◦^ forces centering {2:^10} 1/7/2015CS 4320, SPRING 2015 2

3. Format: Decimal Places For floating point numbers, the format can specify the exact number of decimal places to display The value displayed is rounded from the internal value To specify decimal places, put a decimal point following the field width, or directly following the colon if there is not field width specified After the decimal point, put the number of decimal places desire Follow this with the letter ‘f’ (must be lower case) Note: the number of decimal places is not added to the field width, it is part of the total field width ◦{:10.3f} will use 10 characters total. Of these, one will be a decimal point and 3 will be for decimal places. That leaves six characters for the integer part and a possible negative sign 1/7/2015CS 4320, SPRING 2015 3

4. Comments About Formatting The Format String Syntax section of the Python library documentation gives details about many other options and possibilitiesFormat String Syntax There is a built-in function format that can be used for single values. This can be helpful with web pages since creating columns is done with tags in HTML rather than spacing Do not attempt to format floating point values by using rounding functions. ◦This will often lose precision in calculations, which is not desirable ◦The rounded value will not always display with the expected number of decimal points because of the way floating point arithmetic is carried out 1/7/2015CS 4320, SPRING 2015 4