Python Code Snippets

In most cases, we need format a string before display.

join is the basic function to concatenate strings

just_len = 60
print('join is very useful to concatenate items in tuple'.ljust(just_len),
      ' '.join(('an', 'apple', 'a', 'day')))
print('join is very useful to concatenate items in list'.ljust(just_len),
      ','.join(['keep', 'doctors', 'away']))

or_generator = (s for s in ['that', 'might', 'be', 'true'])
print('join is very useful to concatenate items even generator'.ljust(just_len),
      ' '.join(or_generator), type(or_generator))

Align on the left, padding spaces or another character. only can specify char would work, provide more than one char will raise exception print('ljust mean align on left, padding other chars'.ljust(just_len), text.ljust(20, '*x'))

text = 'Hello World'
print('ljust mean align on left, padding space on right by default'.ljust(just_len),
      text.ljust(20), '*')
print('ljust mean align on left, padding other chars'.ljust(just_len),
      text.ljust(20, '*'))

Align on the right

print('rjust mean align on right, padding space on left by default'.ljust(just_len),
      text.rjust(20))
print('rjust mean align on right, padding other chars'.ljust(just_len),
      text.rjust(20, '*'))

Align center

print('center mean align on center, padding space on left and right'.ljust(just_len),
      text.center(20))
print('center mean align on center, padding other chars'.ljust(just_len),
      text.center(20, '*'))

, <, ^ is just the same with rjust, ljust, center ```python print('format with >, doing the same with rjust'.ljust(just_len), format(text, '>20')) print('format with <, doing the same with ljust'.ljust(just_len), format(text, '<20')) print('format with ^, doing the same with center'.ljust(just_len), format(text, '^20'))

like rjust, ljust, center, padding char can be specified
```python
print('format with =>, the same with rjust padding ='.ljust(just_len),
      format(text, '=>20'))
print('format with =<, the same with ljust padding ='.ljust(just_len),
      format(text, '=<20'))
print('format with =^, the same with center padding ='.ljust(just_len),
      format(text, '=^20'))

format other format is also possible

print('format can be used format other types'.ljust(just_len), format(1.23456, '=>10.2f'))

format is quite powerful to replace values

print('its working, but not easy to read'.ljust(just_len),
      '{} {}'.format('rockie', 'yang'))

print('this format is quite easy to read'.ljust(just_len),
      '{first} {last}'.format(first='rockie', last='yang'))

print('even can replace more than one value regardless order'.ljust(just_len),
      '{last} {first} {last}'.format(first='rockie', last='yang'))

format based on map

first = 'rockie'
last = 'yang'
print('format based on a map, all local variables'.ljust(just_len),
      '{first} {last}'.format_map(vars()))

format based on a object

class Person:
    def __init__(self, first, last):
        self.first = first
        self.last = last

print('format based on a map, like object'.ljust(just_len),
      '{first} {last}'.format_map(vars(Person('rockie', 'yang'))))

safe substitute or substitute in separate steps

class safesub(dict):
    def __missing__(self, key):
        return '{' + key + '}'

print('if we missing some value, or want format with separate steps'.ljust(just_len),
      '{first} {middle} {last}'.format_map(safesub(vars())))

this should be the same with using vars(). but more complex

import sys def sub_with_locals(text): return text.format_map(safesub(sys._getframe(1).f_locals))

print('if we want substitute with frame hack'.ljust(just_len), sub_with_locals('{first} {middle} {last}'))