python - 根据不同数量/长度的值/元组动态格式化字符串

Question

最近我收到了根据不同长度的元组动态格式化字符串的需求。其思想是根据元组值重复填充字符串，直到字符串格式化完成。例如，假设我的字符串格式如下:

"{} {} {} {} {} {}"

我想将内容插入到字符串中，例如:

# For: ("hello",)
'hello hello hello hello hello'  # <- repeated "hello"

# For: ("hello", "world")
'hello world hello world hello'  # <- repeated "hello world"

# For: ("hello", "world", "2017")
'hello world 2017 hello world'   # <- repeated "hello world 2017"

我在这里搜索但找不到任何好的方法来做到这一点，所以想在这里分享。

Answer 1

使用itertools.chain() :

>>> from itertools import chain

>>> my_string = "{} {} {} {} {}"
>>> my_tuple = ("hello", "world")  # tuple of length 2
>>> my_string.format(*chain(my_tuple*6)) # here 6 is some value equal to
'hello world hello world hello'          # maximum number of time for which
                                         # formatting is allowed

或者，我们也可以使用itertools.chain.from_iterator()来做到这一点和 itertools.repeat()如:

>>> from itertools import chain, repeat

>>> my_string.format(*chain.from_iterable(repeat(my_tuple, 6)))
'hello world hello world hello'

元组将不断重复自身，直到填满所有格式字符串。

<小时/>

其他一些示例运行:

# format string of 5
>>> my_string = "{} {} {} {} {}"

### Tuple of length 1
>>> my_tuple = ("hello",)
>>> my_string.format(*chain(my_tuple*6))
'hello hello hello hello hello'

### Tuple of length 2
>>> my_tuple = ("hello", "world")
>>> my_string.format(*chain(my_tuple*6))
'hello world hello world hello'

### Tuple of length 3
>>> my_tuple = ("hello", "world", "2016")
>>> my_string.format(*chain(my_tuple*6))
'hello world 2016 hello world'