Accept-Language = pl,en-us;q=0.7,en;q=0.3

s = dict([a.split('=', 1) for a in s])

ValueError: dictionary update sequence element #0 has length 1; 2 is required

q=0.7,en;q=0.3

s = "Accept-Language = pl,en-us;q=0.7,en;q=0.3"

s = dict([a.split('=', 1) for a in s])

Accept-Language: da, en-gb;q=0.8, en;q=0.7

In [1]: s = 'Accept-Language = pl,en-us;q=0.7,en;q=0.3'
In [2]: dict(item.split(" = ") for item in s.split('\n'))
Out[2]: {'Accept-Language': 'pl,en-us;q=0.7,en;q=0.3'}

s = "Accept-Language = pl"

ValueError: dictionary update sequence element #0 has length 1; 2 is required

In [1]: s = 'Accept-Language = pl,en-us;q=0.7,en;q=0.3'
In [2]: dict(item.split(" = ") for item in s.split('\n'))
Out[2]: {'Accept-Language': 'pl,en-us;q=0.7,en;q=0.3'}

{'Accept-Language': 'pl,en-us;q=0.7,en;q=0.3\r'}