如果未以str.format传递，则将值留空

如果未以str.format传递，则将值留空

您可以遵循PEP 3101中的建议，并使用子类Formatter：

import stringclass BlankFormatter(string.Formatter):    def __init__(self, default=''):        self.default=default    def get_value(self, key, args, kwds):        if isinstance(key, str): return kwds.get(key, self.default)        else: return string.Formatter.get_value(key, args, kwds)kwargs = {"name": "mark", "adj": "mad"}     fmt=BlankFormatter()print fmt.format("My name is {name} and I'm really {adj}.", **kwargs)# My name is mark and I'm really mad.print fmt.format("My name is {name} and I'm really {adjective}.", **kwargs)# My name is mark and I'm really .

---

从Python
3.2开始，您可以使用.format_map作为替代：

class Default(dict):    def __missing__(self, key):        return '{'+key+'}'kwargs = {"name": "mark"}print("My name is {name} and I'm really {adjective}.".format_map(Default(kwargs)))

打印：

My name is mark and I'm really {adjective}.