def is_matched(expr):
"""Return True if all delimiters are properly match; False otherwise."""
lefty = '({[' # opening delimiters
righty = ')}]' # respective closing delimiters
stack = PyListStack()
for c in expr:
if c in lefty:
stack.push(c) # push left delimiter on stack
elif c in righty:
if stack.is_empty():
return False # nothing to match with
if righty.index(c) != lefty.index(stack.pop()):
return False # mismatched
return stack.is_empty() # were all symbols matched?
def is_html_matched(raw):
"""Return True if all HTML tags are properly matched; False otherwise."""
stack = PyListStack()
c1 = raw.find('<') # find first '<' character (if any)
while c1 != -1:
c2 = raw.find('>', c1 + 1) # find next '>' character
if c2 == -1:
return False # invalid tag
tag = raw[c1 + 1:c2] # strip away <>
if not tag.startswith('/'): # this is opening tag
stack.push(tag)
else:
if stack.is_empty():
return False # nothing to match with
if tag[1:] != stack.pop():
return False # mismatched delimiter
c1 = raw.find('<', c2 + 1) # find next '<' character (if any)
return stack.is_empty() # were all opening tags matched?
def is_paren_matched(input_string):
"""Return True if all delimiters are properly match; False otherwise."""
opening_del = '({[' # opening delimiters
closing_del = ')}]' # respective closing delimiters
stack = PyListStack()
for c in input_string:
if c in opening_del:
stack.push(c) # push opening delimiter on stack
elif c in closing_del:
if stack.is_empty():
return False # nothing to match with
else:
top = stack.pop()
if closing_del.index(c) != opening_del.index(top):
return False # mismatched
return stack.is_empty() # were all symbols matched?
def reverse_file(fl_name):
"""Overwrite given file with its contents line-by-line reversed."""
stack = PyListStack()
original_file = open(fl_name)
for line in original_file:
stack.push(line.rstrip('\n')) # re-insert newlines when writing
original_file.close()
# Overwrite with contents in LIFO order
reversed_file = open(fl_name, 'w') # reopening file overwrites original
while not stack.is_empty():
reversed_file.write(stack.pop() + '\n') # re-insert newline characters
reversed_file.close()
def int_to_bin(int_num):
"""Converts integer into binary number using stack."""
stack = PyListStack()
while int_num > 0:
remainder = int_num % 2
stack.push(remainder)
int_num = int_num // 2
bin_num = ""
while not stack.is_empty():
bin_num += str(stack.pop())
return bin_num
def test_is_empty(self):
stack = PyListStack()
assert stack.is_empty() is True
stack.push("A")
assert stack.is_empty() is False