TypeError string indices must be integers not str working with dict

Question

I am trying to define a procedure  involved courses  person   that takes as input a courses structure and a person and returns a Dictionary that describes all the courses the person is involved in   Here is my involved courses  person  function   def involved courses  person       for time1 in courses          for course in courses time1               for info in time1 course                   print info   Here is my dictionary   courses          feb2012      cs101     name    Building a Search Engine                               teacher    Dave                               assistant    Peter C                       cs373     name    Programming a Robotic Car                               teacher    Sebastian                               assistant    Andy          apr2012      cs101     name    Building a Search Engine                               teacher    Dave                               assistant    Sarah                      cs212     name    The Design of Computer Programs                               teacher    Peter N                                assistant    Andy                               prereq    cs101                      cs253                      name    Web Application Engineering - Building a Blog                               teacher    Steve                               prereq    cs101                      cs262                      name    Programming Languages - Building a Web Browser                               teacher    Wes                               assistant    Peter C                                prereq    cs101                      cs373     name    Programming a Robotic Car                               teacher    Sebastian                      cs387     name    Applied Cryptography                               teacher    Dave          jan2044      cs001     name    Building a Quantum Holodeck                               teacher    Dorina                    cs003     name    Programming a Robotic Robotics Teacher                               teacher    Jasper                                   When I m trying to test my code    gt  gt  gt print involved courses   Dave     Python give me an error   for info in time1 course   TypeError  string indices must be integers  not str   How can I fix that   Thanks

User · Answer

I see that you are looking for an implementation of the problem more than solving that error. Here you have a possible solution:

from itertools import chain

def involved(courses, person):
    courses_info = chain.from_iterable(x.values() for x in courses.values())
    return filter(lambda x: x['teacher'] == person, courses_info)

print involved(courses, 'Dave')

The first thing I do is getting the list of the courses and then filter by teacher's name.

User · Answer

time1 is the key of the most outer dictionary  eg  feb2012  So then you re trying to index the string  but you can only do this with integers  I think what you wanted was   for info in courses time1  course     As you re going through each dictionary  you must add another nest

User · Answer

Actually I think that more general approach to loop through dictionary is to use iteritems       get tuples of term  courses for term  term courses in courses iteritems          get tuples of course number  info     for course  info in term courses iteritems              loop through info         for k  v in info iteritems                print k  v   output   assistant Peter C  prereq cs101     name Programming a Robotic Car teacher Sebastian   Or  as Matthias mentioned in comments  if you don t need keys  you can just use itervalues     for term courses in courses itervalues        for info in term courses itervalues            for k  v in info iteritems                print k  v

[python] TypeError: string indices must be integers, not str // working with dict

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