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Python is via datetime.isocalendar() able to produce the ISO week number and ISO weekday from a given date. But it is not possible to do the reverse; calculate the date from a year, ISO week number and weekday.
libc strptime()/strftime() mentions a %V and %u directive which does this, i.e. Monday in ISO week 22 of the year 2011:
 datetime.strptime('2011221', '%Y%V%u')
returning 2011年05月30日 and
 datetime.strptime('2011227', '%Y%V%u')
returning 2011年06月05日
libc (on FreeBSD) has this to say:
%V is replaced by the week number of the year (Monday as the first day
 of the week) as a decimal number (01-53). If the week containing
 January 1 has four or more days in the new year, then it is week 1;
 otherwise it is the last week of the previous year, and the next
 week is week 1.
%u is replaced by the weekday (Monday as the first day of the week) as
 a decimal number (1-7).