I'm assembling a url for an http request

```
baseurl = 'http://..'
action = 'mef'
funcId = 100
year = 2018
month = 1

url = '{}?action={}&functionId={}&yearMonth={}{}'.format(baseurl, action, funcId, year, month)

```

What's bugging me is I need the month number to be padded with a 0 if its less than 10.
I know how to pad a number if its the only variable to format:

```
'{0:02d}'.format(month)  # returns: 01

```

Though when I try this in:

```
'{}?action={}&functionId={}&yearMonth={}{0:02d}'.format(baseurl, action, funcId, year, month)

```

It results in the error:

```
ValueError: cannot switch from automatic field numbering to manual field specification

```

I assumed it's because the other brackets aren't shown what type of variable to expect, but I cant figure out with what character to specify a string.