相关疑难解决方法(0)

我有一个类,其实例需要按照用户的指示格式化输出.有一种默认格式,可以覆盖.我这样实现了:

class A:
  def __init__(self, params):
    # ...
    # by default printing all float values as percentages with 2 decimals
    self.format_functions = {float: lambda x : '{:.2%}'.format(x)}
  def __str__(self):
    # uses self.format_functions to format output
    # ...

a = A(params)
print(a) # uses default output formatting

# overriding default output formatting
# float printed as percentages 3 decimal digits; bool printed as Y / N
a.format_functions = {float : lambda x: '{:.3%}'.format(x),
                      bool : lambda x: 'Y' if x else …