# Week 11 practice problems, by chaynes@indiana.edu

def line_count(file_name):
    """Return the number of lines in the named file.

    >>> print file('data.txt').read()
    3
    5.4
    <BLANKLINE>
    -2
    <BLANKLINE>
    >>> line_count('data.txt')
    4
    >>>
    """
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def copy_lines(in_file_name, out_file_name, start_string, stop_string):
    """Copy lines from the input file to the output file, starting with
    the first line containing the start string and stopping when a line
    containing the stop string is read (without writing the stop string
    line).

    If start_string is not in the file, do not even open the output file,
    and if the stop string is not found, write to the end of the input
    file.

    >>> print file('argument.txt').read()
    M: When? 
    O: Just now. 
    M: No you didn't! 
    O: Yes I did! 
    M: You didn't! 
    O: I did! 
    M: You didn't! 
    <BLANKLINE>
    >>> copy_lines('argument.txt', 'subargument.txt', 'Just', 'I did')
    >>> print file('subargument.txt').read()
    M: When? 
    O: Just now. 
    M: No you didn't! 
    <BLANKLINE>
    >>>
    """
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import csv

def print_column(csv_file_name, column_index):
    """Print, one per line, the values in the indicated column of the table in
    the Csv file. Use zero-based indexing of the columns.

    >>> print file('contacts.csv').read()
    First Name,Last Name,Suffix,Home Street,Home Street 2,Home City,Home State,Home Postal Code,Telex
    Sally,Porter,,4324 Hedrick Ln,,Jersy City,NJ,23403,HB
    Sam,Proxmire,,125 Hampton Cr,,Jefferson,NY,32084,BA
    Sue,Pinter,,32 Hawthorn Dr,,Jackson,MS,13034,HB
    <BLANKLINE>
    >>> print_column('contacts.csv', 3)
    Home Street
    4324 Hedrick Ln
    125 Hampton Cr
    32 Hawthorn Dr
    >>>
    """
    # Hint: use csv module information in assignment 11.
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def differences(lst):
    """Return a list of numbers that are the differences between each successive
    pair of values in lst. More precisely, the i_th value in the returned list
    is the difference between the (i+1)_th and i_th values in the given
    list. The returned list is thus one shorter than lst, which may be assumed
    to contain at least two values. (This is the discrete counterpart of the 
    derivative of continuously varying functions in mathematics.)

    >>> differences([1, 0, 5, 3])
    [-1, 5, -2]
    >>>
    """
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def delete_ends(lst):
    """Delete the first and last elements of lst.
    
    >>> los = list('abcd')
    >>> delete_ends(los)
    >>> los
    ['b', 'c']
    >>>
    """
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def delete_duplicates(lst):
    """Delete elements from lst so that no two elements have the same value, but
    every value that was in lst initially still remains (but only once). The
    values in the resulting list are in the order of their first appearance in
    the given lst.
    
    >>> a = list('adabbaacd')
    >>> delete_duplicates(a)
    >>> a
    ['a', 'd', 'b', 'c']
    >>>
    """
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