May 10, 2021 Python2
String formatting allows multiple specific types of substitutions to be performed on a string in a single step
Especially when giving tips to users, formatting is very convenient
How to implement it:
1. Format the expression, similar to the printf in the c language
In an expression, we use the % binary operator
>>> print('this is %d %s bird' % (1,'dead'))
this is 1 dead bird
Take the example above (note that the % we're talking about below is based on the one in the middle of the string and the metagroup)
Place a string on the left side of % that contains one or more embedded objects that start with %
Put one (or more) objects on the right side of % that are embedded in the metagroup, which are inserted into the conversion target position on the left
>>> name='ray'
>>> 'my name is %s' % name
'my name is ray'
>>> '%d %s %d you' % (1,'spam',4)
'1 spam 4 you'
>>> '%s---%s---%s' % (42,3.14,[1,2,3])
'42---3.14---[1, 2, 3]'
>>> When you insert multiple objects, you need to put them in a single group
2. Advanced formatting expressions
The string formats the list of code
| Code | Significance |
|---|---|
| s | String (or any object) |
| R | s, but with repr, not str |
| C | Character |
| D | A hedding integer |
| Ⅰ | Integer |
| u | No integer |
| O | Octal integers |
| Ⅹ | Hetey integers |
| Ⅹ | x, but print capital |
| E | Floating-point index |
| E | e, but print capital |
| F | Floating-point hete ten-party system |
| F | Floating-point hete ten-party system |
| G | Floating point e or f |
| G | Floating point e or f |
| % | Constant % |
%[(name)][flags][width][.pression]typecode
Example
>>> x=1234
>>> res='integers:...%d...%-6d...%06d' % (x,x,x)
>>> res
'integers:...1234...1234 ...001234'
>>> %e, %f, %g are different for floating-point printing
>>> x=1.23456789
>>> x
1.23456789
>>> '%e|%f|%g' % (x,x,x)
'1.234568e+00|1.234568|1.23457'
>>> 3. Dictionary-based formatted expressions
>>> 'my name is %(name)s,my age is %(age)d' % {'name':'ray','age':30}
'my name is ray,my age is 30'
>>> To put it actually, name each replacement location so that the code looks clearer