python关键字字符串格式与'％'混淆错误：不支持的格式字符'p'

Question

I have the following setup

cred_dict={'admin_id':'user','admin_password':'pass'}

cred_template='-id=%(admin_id) -pa=%(admin_password)'

When I try

cred_template % cred_dict

I get

ValueError: unsupported format character 'p' (0x70) at index 17

and I can't figure out why.

Answer 1

You are missing a crucial element: the formatting type indicator:

cred_template='-id=%(admin_id)s -pa=%(admin_password)s'
#                             ^                      ^

The s indicates you want to format the values as strings. Without those indicators, Python keeps looking for the type and finds the letter p (from -pa ) and that's not a valid type indicator.

Demo:

>>> cred_dict={'admin_id':'user','admin_password':'pass'}
>>> cred_template='-id=%(admin_id)s -pa=%(admin_password)s'
>>> cred_template % cred_dict
'-id=user -pa=pass'

Answer 2

You can also use str.format which you may find easier and less error prone:

cred_dict={'admin_id':'user','admin_password':'pass'}    
cred_template='-id={admin_id} -pa={admin_password}'
print(cred_template.format(**cred_dict))

-id=user -pa=pass