def extract_name(s):
"""
Returns the first name of the person in e-mail address s.
We assume (see the precondition below) that the e-mail address is in one of
two forms:
[email protected]
[email protected]
where first and last correspond to the person's first and last name. Names
are not empty, and contain only letters. Everything after the @ is guaranteed
to be exactly as shown.
The function preserves the capitalization of the e-mail address.
Examples:
extract_name('*****@*****.**') returns 'john'
extract_name('*****@*****.**') returns 'maggie'
extract_name('*****@*****.**') returns 'Bob'
Parameter s: The e-mail address to extract from
Precondition: s is in one of the two address formats described above
"""
# You must use an if-else statement in this function.
if 'com' in s:
idx = introcs.find_str(s, '.')
idx_ = introcs.find_str(s, '@')
first_name = s[idx + 1:idx_]
else:
idx = introcs.find_str(s, '.')
first_name = s[:idx]
return first_name
def first_vowel(s):
"""
Returns the position of the first vowel in s; it returns -1 if there are no vowels.
We define the vowels to be the letters 'a','e','i','o', and 'u'. The letter
'y' counts as a vowel only if it is not the first letter in the string.
Examples:
first_vowel('hat') returns 1
first_vowel('grrm') returns -1
first_vowel('sky') returns 2
first_vowel('year') returns 1
Parameter s: the string to search
Precondition: s is a nonempty string with only lowercase letters
"""
result = len(s)
vowels = ['a', 'e', 'i', 'o', 'u']
for x in vowels:
if x in s:
result = min(result, introcs.find_str(s, x))
if not x in s and "y" in s and introcs.rfind_str(s, "y") != 0:
result = introcs.rfind_str(s, "y")
return result if result != len(s) else -1
def get_src(json):
"""
Returns the src value in the response to a currency query.
Given a JSON string provided by the web service, this function returns the string
inside string quotes (") immediately following the substring '"src"'. For example,
if the json is
'{"success": true, "src": "2 United States Dollars", "dst": "1.772814 Euros", "error": ""}'
then this function returns '2 United States Dollars' (not '"2 United States Dollars"').
On the other hand if the json is
'{"success":false,"src":"","dst":"","error":"Source currency code is invalid."}'
then this function returns the empty string.
The web server does NOT specify the number of spaces after the colons. The JSON
'{"success":true, "src":"2 United States Dollars", "dst":"1.772814 Euros", "error":""}'
is also valid (in addition to the examples above).
Parameter json: a json string to parse
Precondition: json a string provided by the web service (ONLY enforce the type)
"""
assert type(json) == str, 'Precondition violation'
idx = introcs.find_str(json, "src")
src = first_inside_quotes(json[idx + 5:])
return src
def exchange(src, dst, amt):
"""
Returns the amount of currency received in the given exchange.
In this exchange, the user is changing amt money in currency src to the currency
dst. The value returned represents the amount in currency currency_to.
The value returned has type float.
Parameter src: the currency on hand
Precondition src is a string for a valid currency code
Parameter dst: the currency to convert to
Precondition dst is a string for a valid currency code
Parameter amt: amount of currency to convert
Precondition amt is a float or int
"""
assert type(src) == str and len(src) == 3, 'Precondition violation'
assert introcs.count_str(src, " ") == 0, 'Precondition violation'
assert type(dst) == str and len(dst) == 3, 'Precondition violation'
assert introcs.count_str(dst, " ") == 0, 'Precondition violation'
assert type(amt) == float or type(amt) == int, 'Precondition violation'
response = service_response(src, dst, amt)
idx = introcs.find_str(response, "dst")
convert_to = first_inside_quotes(response[idx + len("dst") + 1:])
amt_received = before_space(convert_to)
value = float(amt_received)
return value
def valid_format(s):
"""
Returns True if s is a string in 12-format <hours>:<min> AM/PM
Example:
valid_format('2:45 PM') returns True
valid_format('2:45PM') returns False
valid_format('14:45') returns False
valid_format('14:45 AM') returns False
valid_format(245) returns False
Parameter s: the candidate time to format
Precondition: NONE (s can be any value)
"""
if type(s) != str:
return False
colon = introcs.find_str(s, ':')
if colon == -1:
return False
elif not introcs.isdigit(s[:colon]) or not introcs.isdigit(
s[colon + 1:colon + 3]):
return False
hrs = int(s[:colon])
mins = int(s[colon + 1:colon + 3])
if hrs < 1 or hrs > 12 or mins >= 60:
return False
return s[colon + 3:] == ' AM' or s[colon + 3:] == ' PM'
def has_error(json):
"""
Returns True if the response to a currency query encountered an error.
Given a JSON string provided by the web service, this function returns True if the
query failed and there is an error message. For example, if the json is
'{"success":false,"src":"","dst":"","error":"Source currency code is invalid."}'
then this function returns True (It does NOT return the error message
'Source currency code is invalid'). On the other hand if the json is
'{"success": true, "src": "2 United States Dollars", "dst": "1.772814 Euros", "error": ""}'
then this function returns False.
The web server does NOT specify the number of spaces after the colons. The JSON
'{"success":true, "src":"2 United States Dollars", "dst":"1.772814 Euros", "error":""}'
is also valid (in addition to the examples above).
Parameter json: a json string to parse
Precondition: json a string provided by the web service (ONLY enforce the type)
"""
assert type(json) == str, 'Precondition violation'
idx = introcs.find_str(json, "error")
error = first_inside_quotes(json[idx + 6:])
result = bool(error)
return result
def time_to_minutes(s):
"""
Returns the number of minutes since midnight
Examples:
time_to_minutes('2:45 PM') returns 885
time_to_minutes('9:05 AM') returns 545
time_to_minutes('12:00 AM') returns 0
Parameter s: string representation of the time
Precondition: s is a string in 12-format '<hours>:<min> AM/PM'
"""
assert valid_format(s) == True
#find the positions
pos1 = introcs.find_str(s, ":")
pos2 = introcs.find_str(s, " ")
hour = str(s[:pos1])
time = s[pos2 + 1:]
currMin = int(s[pos1 + 1:pos2])
# assert type(s) == str
# assert 7 <= len(s) <= 8
# assert currMin <= 60
# assert 1 <= int(hour) <= 12
# assert introcs.find_str(s,":") != -1
# assert introcs.find_str(s," ") != -1
# convert hour to minutes
hour = str(s[:pos1])
time = s[pos2 + 1:]
currMin = int(s[pos1 + 1:pos2])
if time == 'PM' and hour != '12':
hour = int(hour)
hour += 12
min = int(hour) * 60
currMin += min
elif time == 'AM' and hour == '12':
hour = 0
min = int(hour) * 60
currMin += min
else:
min = int(hour) * 60
currMin += min
return currMin
def first_vowel(s):
"""
Returns the position of the first vowel in s; it returns -1 if there are no vowels.
We define the vowels to be the letters 'a','e','i','o', and 'u'. The letter
'y' counts as a vowel only if it is not the first letter in the string.
Examples:
first_vowel('hat') returns 1
first_vowel('grrm') returns -1
first_vowel('sky') returns 2
first_vowel('year') returns 1
Parameter s: the string to search
Precondition: s is a nonempty string with only lowercase letters
"""
result = len(s) # In case there is no 'a'
if 'a' in s:
result = introcs.find_str(s, 'a')
if 'e' in s[:result]:
result = introcs.find_str(s, 'e')
if 'i' in s[:result]:
result = introcs.find_str(s, 'i')
if 'o' in s[:result]:
result = introcs.find_str(s, 'o')
if 'u' in s[:result]:
result = introcs.find_str(s, 'u')
if 'y' in s[1:result]:
result = introcs.find_str(s, 'y')
return -1 if (result == len(s) and 'y' not in s[1:]) else result
def get_dst(json):
"""
Returns the dst value in the response to a currency query.
Given a JSON string provided by the web service, this function returns the string
inside string quotes (") immediately following the substring '"dst"'. For example,
if the json is
'{"success": true, "src": "2 United States Dollars", "dst": "1.772814 Euros", "error": ""}'
then this function returns '1.772814 Euros' (not '"1.772814 Euros"'). On the other
hand if the json is
'{"success":false,"src":"","dst":"","error":"Source currency code is invalid."}'
then this function returns the empty string.
The web server does NOT specify the number of spaces after the colons. The JSON
'{"success":true, "src":"2 United States Dollars", "dst":"1.772814 Euros", "error":""}'
is also valid (in addition to the examples above).
Parameter json: a json string to parse
Precondition: json a string provided by the web service (ONLY enforce the type)
"""
pos1 = introcs.find_str(json, '"')
pos2 = introcs.find_str(json, '"', pos1 + 1)
pos3 = introcs.find_str(json, '"', pos2 + 1)
pos4 = introcs.find_str(json, '"', pos3 + 1)
pos5 = introcs.find_str(json, '"', pos4 + 1)
pos6 = introcs.find_str(json, '"', pos5 + 1)
pos7 = introcs.find_str(json, '"', pos6 + 1)
pos8 = introcs.find_str(json, '"', pos7 + 1)
pos9 = introcs.find_str(json, '"', pos8 + 1)
pos10 = introcs.find_str(json, '"', pos9 + 1)
return json[pos9 + 1:pos10]
def first_inside_quotes(s):
"""
Returns the first substring of s between two (double) quote characters
Note that the double quotes must be part of the string. So "Hello World" is a
precondition violation, since there are no double quotes inside the string.
Example: first_inside_quotes('A "B C" D') returns 'B C'
Example: first_inside_quotes('A "B C" D "E F" G') returns 'B C', because it only
picks the first such substring.
Parameter s: a string to search
Precondition: s is a string with at least two (double) quote characters inside
"""
assert type(s) == str
pos1 = introcs.find_str(s, '"')
assert pos1 >= 0
pos2 = introcs.find_str(s, '"', pos1 + 1)
assert pos2 >= pos1 + 1
return s[pos1 + 1:pos2]
def after_space(s):
"""
Returns the substring of s after the first space
Example: after_space('Hello World') returns 'World'
Parameter s: the string to slice
Precondition: s is a string with at least one space in it
"""
assert type(s) == str, "Invalide type"
# assert introcs.find_str(s, ' ') == True
index = introcs.find_str(s, ' ')
assert index >= 0
after = s[index + 1:]
return after
def before_space(s):
"""
Returns the substring of s up to, but not including, the first space.
Example: before_space('Hello World') returns 'Hello'
Parameter s: the string to slice
Precondition: s is a string with at least one space in it
"""
assert introcs.count_str(s, " ") != 0, 'Precondition violation'
idx = introcs.find_str(s, ' ')
sub = s[:idx]
return sub
def after_space(s):
"""
Returns the substring of s after the first space
Example: after_space('Hello World') returns 'World'
Parameter s: the string to slice
Precondition: s is a string with at least one space in it
"""
assert introcs.count_str(s, " ") != 0, 'Precondition violation'
idx = introcs.find_str(s, ' ')
sub = s[idx + 1:]
return sub
def before_space(s):
"""
Returns the substring of s up to, but not including, the first space.
Example: before_space('Hello World') returns 'Hello'
Parameter s: the string to slice
Precondition: s is a string with at least one space in it
"""
assert type(s) == str, "Input must be a string"
# assert introcs.find_str(s, ' ') == True
index = introcs.find_str(s, ' ')
assert index >= 0
before = s[0:index]
return before
def iscurrency(currency):
"""
Returns True if currency is a valid (3 letter code for a) currency.
It returns False otherwise.
Parameter currency: the currency code to verify
Precondition: currency is a nonempty string with only letters
"""
assert type(currency) == str and len(
currency) == 3, 'Precondition violation'
response = service_response(currency, currency, 1)
idx = introcs.find_str(response, "error")
errormessage = first_inside_quotes(response[idx + len("error") + 1:])
result = not bool(errormessage)
return result
def iseurofloat(s):
"""
Returns True if s is a float in European format. Returns False otherwise.
In European format, a comma is used in place of a decimal point. So '12,5' stands
for 12.5, '0,12' stands for 0.12 and so. Formally, a string is in European format
if it is of the form <d1>,<d2> where d1 and d2 are ints (and d2 >= 0). See
https://en.wikipedia.org/wiki/Decimal_separator
for more information.
This function does not recognize floats in scientific notation (e.g. '1e-2').
Examples:
iseurofloat('12,5') returns True
iseurofloat('-12,5') returns True
iseurofloat('12') returns False
iseurofloat('12,-5') returns False
iseurofloat(',5') returns False
iseurofloat('apple') returns False
iseurofloat('12,5.3') returns False
iseurofloat('12,5,3') returns False
iseurofloat('1e-2') returns False
Parameter s: The string to check
Precondition: s is a string
"""
# You MAY NOT use conditionals anywhere in this function.
result = False
pos1 = introcs.find_str(s, ",")
try:
assert pos1 != -1
before_comma = s[:pos1]
after_comma = s[pos1 + 1:]
assert int(after_comma) >= 0
0 > int(before_comma) > 0 and int(after_comma) > 0
result = True
except:
result = False
return result
def has_error(json):
"""
Returns True if the response to a currency query encountered an error.
Given a JSON string provided by the web service, this function returns True if the
query failed and there is an error message. For example, if the json is
'{"success":false,"src":"","dst":"","error":"Source currency code is invalid."}'
then this function returns True (It does NOT return the error message
'Source currency code is invalid'). On the other hand if the json is
'{"success": true, "src": "2 United States Dollars", "dst": "1.772814 Euros", "error": ""}'
then this function returns False.
The web server does NOT specify the number of spaces after the colons. The JSON
'{"success":true, "src":"2 United States Dollars", "dst":"1.772814 Euros", "error":""}'
is also valid (in addition to the examples above).
Parameter json: a json string to parse
Precondition: json a string provided by the web service (ONLY enforce the type)
"""
pos1 = introcs.find_str(json, '"')
pos2 = introcs.find_str(json, '"', pos1 + 1)
pos3 = introcs.find_str(json, '"', pos2 + 1)
pos4 = introcs.find_str(json, '"', pos3 + 1)
pos5 = introcs.find_str(json, '"', pos4 + 1)
pos6 = introcs.find_str(json, '"', pos5 + 1)
pos7 = introcs.find_str(json, '"', pos6 + 1)
pos8 = introcs.find_str(json, '"', pos7 + 1)
pos9 = introcs.find_str(json, '"', pos8 + 1)
pos10 = introcs.find_str(json, '"', pos9 + 1)
pos11 = introcs.find_str(json, '"', pos10 + 1)
pos12 = introcs.find_str(json, '"', pos11 + 1)
pos13 = introcs.find_str(json, '"', pos12 + 1)
pos14 = introcs.find_str(json, '"', pos13 + 1)
finalVal = len(json[pos13 + 1:pos14])
return finalVal > 0
