def count_char(input):
    '''
    Counts the number of occurrences of each character in a string. The result should be a dictionary where the key is the character and the dictionary is its count.

    For example,
    >>> count_char("HelloOo!")
    {'H': 1, 'e': 1, 'l': 2, 'o': 2, 'O': 1, '!': 1}
    '''
    d = {}
    # d = {'H': 1
    for c in input:
     if c in d: # Is a key named 'H' inside the d?
      d[c] = d[c] + 1 #then count 'H'
     else:
      d[c] = 1 #if there's no 'H' then make the value as 1

    return d
    #pass
"""
def test_count_char():
  assert count_char("HelloOo!") == {'H': 1, 'e': 1, 'l': 2, 'o': 2, 'O': 1, '!': 1}
def test_empty():
    assert count_char("") == {}

def test_simple():
    assert count_char("abc") == {"a": 1, "b": 1, "c": 1}

def test_double():
    assert count_char("aa") == {"a": 2}

def test_uppercase():
    assert count_char("aA") == {"a": 1, "A": 1}
def test_space():
    assert count_char("Hi a") == {"H": 1, "i": 1, " ": 1, "a": 1}
"""