Simple part
The rules of the game
OK let’s first think about how we can go about doing this.
We have two separate arguments so we need to turn them into writing one-by-one.
We need to check which number our input corresponds to and return a writing.
- Instead of checking them one by one (
if input == 1,if input == 2etc.) we can use lists- We’ll make a list such that
our_list[number] == number in writing.
- We’ll make a list such that
- We need to check for the “weird” numbers in the English language between 10 and 20. (15 = fifteen and not ten five)
Alright with these rules let’s start building our function. First we write the definition line and then we indent
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def time2words(hour, minute):
#indented
Wordlists
Now we need to make our wordlists. This may seem daunting since there are 60 different numbers we need to come up with but actually, we don’t need to define them all. We can just define the ones (1,2,3,4…) and tens (10, 20, 30, 40…) and then we can use both of these lists at once to express numbers like 45 (forty + five).
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ones = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['ten', 'twenty', 'thirty', 'forty', 'fifty']
But there’s a slight problem here. Because this doesn’t abide the way we had things in mind in our 3rd rule. We want to have a list so that ones[1]=='one' but here we clearly have ones[1]=='two' because lists start from 0. So we slightly adjust our list.
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ones = ['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['zero', 'ten', 'twenty', 'thirty', 'forty', 'fifty']
But it’s still not quite right. How might we express a time like 03:00? 3 am. So we don’t even ever say the 'zero' part. We just leave it blank. Let’s change our lists to reflect this.
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ones = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['', 'ten', 'twenty', 'thirty', 'forty', 'fifty']
But these lists will only be useful for the minute part (actually you can adjust them to be useful for the hours part too but I’m not gonna do that so this solution is not too complicated to follow.) We need to make a list of hours too. How about
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hours = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
This is good but again we need to modify it so we can have hours[hour]==hour in writing.
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hours = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
The problem now is, 00:21 is “twelve twenty one am” and not “twenty one am” so we need to change our first item to be 'twelve'.
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hours = ['twelve', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
With our wordlists in place, we can now move on to translation.
Translating hours
Translating hours is very easy since we defined our lists “right”.
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hour_writing = hours[hour]
But this has a big problem. What about the hours after 12? Our function takes 24-hour format and outputs 12-hour format. And our hours list only has hours until 12. So if we try to do hours[15] then we’ll get a nasty IndexError.
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Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IndexError: list index out of range
To prevent this is easy. Think about it. How do we humans know that 15 is 3? Practically we just subtract 12 from 15. So maybe we can do
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if hour > 12:
hour_writing = hours[hour-12]
else:
hour_writing = hours[hour]
This is a valid solution but can we make it better? What else gives us 3 from 15? How about mod 12? You see, 15%12=3 and 3%12=3 so if we use mod, we won’t even need to branch. Let’s replace the last part with
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hour_writing = hours[hour%12]
So now what will happen? For example if we do time2words(15, 30) then hour_writing == hours[15%12]. 15%12 is 3 so hours_writing will be equal to the 3rd (4th in human terms) element of the hours list. The last thing for us to do in this section is to adjust the am or pm parts. How about
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if hour > 12:
appendix = 'pm'
else:
appendix = 'am'
This is good but like everything, it’s not quite right. The problem is that 12:00 (hour > 12) is “twelve pm” and 00:00 (hour < 12) is “twelve am.” With our current model 12:00 will be “twelve am” while 00:00 is “twelve am,” and time2words(24, 0) is “twelve pm.” We need to first check whether hour == 12 or 24 and do things differently if that’s the case.
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if hour == 24:
appendix = 'am'
elif hour == 12:
appendix = 'pm'
elif hour > 12:
# Note how this part won't even be checked if any of the statements above is checked.
appendix = 'pm'
else:
appendix = 'am'
So now first the interpreter checks whether hour==24 if it is, then it’ll skip the others (which is good because we don’t want the 3rd elif statement to run). Check extra for a better way to do this. This concludes the part on hours.
Translating minutes
With minutes we have two parts. The tens part and the ones part. For example with 52 we have 50 + 2. How might we separate 50 and 2 from 52? Let’s start with the ones part
Ones
Here we need to discard the tens part. The easy way to do this is to take the mod 10 of our minute. With this, we’ll get 52%10==2 for example.
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ones_minute = minute%10
Now we have the ones part captured in a variable, we can translate it to words. This translation will be done by finding the value in our ones list (just like we found the hour in hours list).
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ones_minute_writing = ones[ones_minute]
The ones part is effectively over.
Tens
Now how do we get the 50 from 52? Well we already have 2, so why don’t we just subtract it to get the tens part? (52-2=50 which is what we want now)
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tens_minute = minute-ones_minute
Now we can’t translate this as easily as the ones part because tens_minute[50] doesn’t exist. (We only have 6 elements in our tens list) So we need to take the 5 from 50. This is easy to do since we only need to divide our number by 10.
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tens_minute_num = tens_minute/10
But no, this doesn’t work. Because tens_minute/10 is a float and not an integer. And we can’t use floats as indices to lists. To fix this is easy
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tens_minute_num = tens_minute//10
With integer division we’ll always get an integer as a result. Now we need to translate this number to writing and we’ll do it the way we did before.
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tens_minute_writing = tens[tens_minute_num]
Putting it all together
Weird part (10-20)
Putting this all together would be very simple if English wasn’t so weird. But it is. With our current model 15 is “ten five” and not “fifteen.” When we’re returning our output, we need to take care of this with an if statement.
So when the minute is between 10 and 20, we want to return a modified time.
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if 10 < minute < 20:
We need to make a wordlist like we did for the hours and minutes, only this time it’ll be for the “weird” words.
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weird = ['', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen']
(This part is double indented [8 spaces]) I’m sure you get why we make our first element '' now. You see, we already have all the possible numbers between 10 and 20 in our list but weird[number] doesn’t exist because our list doesn’t have that many elements. How can we fix this? Well we can use our ones_minute variable we stored earlier. Because for example if we have 11 then ones_minute == 1 and weird[ones_minute] is “eleven.”
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weird_writing = weird[ones_minute]
At last we return our full string
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return hour_writing+' '+weird_writing+' '+appendix
But our work isn’t over since we only defined what the function will return when there is a weird number. How about when there isn’t one?
Regular returning
We made the weird part with an if statement and it’s only right that we continue this part with an else statement. But note that you don’t actually need this. Because if the if part runs, then the function will return something and interpreter won’t read the rest of the function. (The interpreter doesn’t read what’s written in a function after it sees the return line)
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else:
We can simply return what we have in order
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return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
This will work. But if we care at all about aesthetics we got work to do. You see there’s a possibility that tens_minute_writing or ones_minute_writing to be '' in fact they can both be '' at the same time and then we’ll have too many spaces lying around. For example time2words(15, 0)=='three pm'. But we can fix this with branching.
First let’s think about what different minute types we can have
- 00
- X0
- XY
Where X=Y is a possibility.
So remove the last thing we added. Now, we’ll handle the case where both of our variables is '' (case 1).
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if ones_minute_writing == '' and tens_minute_writing == '':
return hour_writing+' '+appendix
Since our variables are empty strings we don’t even need to include them.
Now we’ll handle the case where ones_minute is 0 but tens_minute isn’t (case 2). If you know some logic then it’ll be easy for you to understand this.
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elif (ones_minute_writing == '') and (tens_minute_writing != ''):
And we return our string (this time adding 2 spaces - no need to add ones_minute_writing since that’s just ''.)
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return hour_writing+' '+tens_minute_writing+' '+appendix
And our last case is the one we thought of first. This time neither ones_minute nor tens_minute is 0.
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else:
return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
We can just use else here because we’re out of options. Aaand we’re done. That was it.
Code in full w/ Comments
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def time2words(hour, minute):
#define our words
#we take the empty string first before because we want ones[1] = "one"
#you dont need to really define your wordlist this way but this seems easier to read / easier to implement so we'll go with this
#if time is 15:00 then it's just 3 am
ones = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['', 'ten', 'twenty', 'thirty', 'forty', 'fifty']
#Notice how ones[1] = 'one' and ones[4] = 'four' because ones[0] = ''
#The GAME PLAN: We will find the hour in our lists and return it. Then we'll find the minute in our lists and return it.
# HOUR PART
hours = ['twelve', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
# This list like all our lists is conveniently set up. Because hours[12] = 'twelve' and hours[2] = 'two'
# So hours[hour] will give us hour in writing if the hour is lower than 12 but what happens if the hour is 15?
# Then hours[15] does not exist and it will give us an error. What can we do?
# We can divide by 12 and get the remainder. Meaning: We can use 'mod 12'. 15 mod 12 = 3 and 3 mod 12 is also 3
# So this certainly fits in with what we want to do.
hour_writing = hours[hour%12]
# The last thing for us to do is to determine whether we are in the am or pm
# This is rather simple. We just need to check whether hour is bigger than 12
# Although we have a problem because 24.00 is 12 am not pm and 12.00 is 12 am not pm
# We can fix this with multiple branches.
if hour == 24:
appendix = 'am'
elif hour == 12:
appendix = 'pm'
elif hour > 12:
# Note how this part won't even be checked if any of the statements above is checked.
appendix = 'pm'
else:
appendix = 'am'
# MINUTE PART
# Find the ones part of our minute.
#When we get the remainder from diving a number by 10, we get the ones part.
# For example: 52 = 5*10+2 so 52 mod 10 = 2.
ones_minute = minute%10
# Now we need to find the word that corresponds with this ones part. Luckily our list is conveniently set up.
# So whatever one_minute might be, ones[ones_minute] is ones_minute in writing
# For example if minute=52 then ones_minute=2 and ones[2]='two'
ones_minute_writing = ones[ones_minute]
# Let's get the tens part now. We can do this by simply subtracting the ones_minute from minute
tens_minute = minute-ones_minute
# Unfortunately we can't do the same trick we did with ones_minute here to get the word part
# Because we'll be getting tens[50] if our number is 52. But this can be easily solved
# We'll just divide tens_minute by 10 to get the number part of it
# So if tens_minute is 50, we'll get 5 by dividing that and tens[5]='fifty' so it will work out.
tens_minute_num = tens_minute//10
# You may find it odd that we use integer division here but the reason is that regular division will return a float
# And we can't use floats as indices.
tens_minute_writing = tens[tens_minute_num]
# Putting it all together
# Now we can simply return hour_writing, tens_minute_writing, ones_minute_writing
# But our problem here is with the English language. Because 15 is "fifteen" not ten five.
# We'll first make an if statement to check for this and fix our words accordingly.
if 10 < minute < 20:
# Make a list of our 'weird' words
weird = ['', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen']
# This list is also conveniently set up but it just needs a little work.
# Notice how with our new list, weird[1] = 'eleven'
# So we can just do weird[ones_minute] to get the word version of a number
weird_writing = weird[ones_minute]
#And now we'll return the full word part
return hour_writing+' '+weird_writing+' '+appendix
else:
# Now we'll return the regular. Note that if the minute isn't between 10 and 20 we haven't returned anything yet.
# return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
# But we must be aware that if tens_minute_writing or ones_minute_writing is '' then there will be too many spaces
# We can fix that with a nested if statement
if ones_minute_writing == '' and tens_minute_writing == '':
# This will only work when both of the writings are ''
return hour_writing+' '+appendix
elif (ones_minute_writing == '') and (tens_minute_writing != ''):
# This will work when ones_minute_writing is '' but tens_minute_writing isn't.
return hour_writing+' '+tens_minute_writing+' '+appendix
else:
return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
Code in full w/o Comments
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def time2words(hour, minute):
ones = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['', 'ten', 'twenty', 'thirty', 'forty', 'fifty']
hours = ['twelve', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
hour_writing = hours[hour%12]
if hour == 24:
appendix = 'am'
elif hour == 12:
appendix = 'pm'
elif hour > 12:
appendix = 'pm'
else:
appendix = 'am'
ones_minute = minute%10
ones_minute_writing = ones[ones_minute]
tens_minute = minute-ones_minute
tens_minute_num = tens_minute//10
tens_minute_writing = tens[tens_minute_num]
if 10 < minute < 20:
weird = ['', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen']
weird_writing = weird[ones_minute]
return hour_writing+' '+weird_writing+' '+appendix
else:
if ones_minute_writing == '' and tens_minute_writing == '':
return hour_writing+' '+appendix
elif (ones_minute_writing == '') and (tens_minute_writing != ''):
return hour_writing+' '+tens_minute_writing+' '+appendix
else:
return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
Extra
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appendix = 'am'
if 24 > hour >= 12:
appendix = 'pm'
Here we pre-define appendix to be 'am' and override it when required (that is, when hour is between 24 and 12 or 12)
Advanced part
For the advanced part only difference is that we need to find a way to convert our time_string to two variables: hour and minute. And like we’re gonna see this week, this is done by slicing the string. We need to split by the : character. Since we know that there’s only one, this will be easy.
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time_list = time_string.split(':')
hour = int(time_list[0])
minute = int(time_list[1])
As you see, the split method is used to split strings into lists. So for example
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>>> time_string = '15:15'
>>> time_string.split(':')
['15', '15']
>>> time_list[0]
'15'
>>> time_list[1]
'15'
>>> int(time_list[0])
15
>>> int(time_list[1])
15
We just need to adjust our function’s arguments and add this snippet to the beginning to complete the advanced part.
Code in full w/ Comments
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def time2words(time_string):
# PREPARATION
# We'll just get the hour and minute variables by breaking up time_string.
# We need to split by the ':' character. Since we know that there's only one, this will be easy.
time_list = time_string.split(':')
hour = int(time_list[0])
minute = int(time_list[1])
#define our words
#we take the empty string first before because we want ones[1] = "one"
#you dont need to really define your wordlist this way but this seems easier to read / easier to implement so we'll go with this
#if time is 15:00 then it's just 3 am
ones = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['', 'ten', 'twenty', 'thirty', 'forty', 'fifty']
#Notice how ones[1] = 'one' and ones[4] = 'four' because ones[0] = ''
#The GAME PLAN: We will find the hour in our lists and return it. Then we'll find the minute in our lists and return it.
# HOUR PART
hours = ['twelve', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
# This list like all our lists is conveniently set up. Because hours[12] = 'twelve' and hours[2] = 'two'
# So hours[hour] will give us hour in writing if the hour is lower than 12 but what happens if the hour is 15?
# Then hours[15] does not exist and it will give us an error. What can we do?
# We can divide by 12 and get the remainder. Meaning: We can use 'mod 12'. 15 mod 12 = 3 and 3 mod 12 is also 3
# So this certainly fits in with what we want to do.
hour_writing = hours[hour%12]
# The last thing for us to do is to determine whether we are in the am or pm
# This is rather simple. We just need to check whether hour is bigger than 12
# Although we have a problem because 24.00 is 12 am not pm and 12.00 is 12 am not pm
# We can fix this with multiple branches.
if hour == 24:
appendix = 'am'
elif hour == 12:
appendix = 'pm'
elif hour > 12:
# Note how this part won't even be checked if any of the statements above is checked.
appendix = 'pm'
else:
appendix = 'am'
# MINUTE PART
# Find the ones part of our minute.
#When we get the remainder from diving a number by 10, we get the ones part.
# For example: 52 = 5*10+2 so 52 mod 10 = 2.
ones_minute = minute%10
# Now we need to find the word that corresponds with this ones part. Luckily our list is conveniently set up.
# So whatever one_minute might be, ones[ones_minute] is ones_minute in writing
# For example if minute=52 then ones_minute=2 and ones[2]='two'
ones_minute_writing = ones[ones_minute]
# Let's get the tens part now. We can do this by simply subtracting the ones_minute from minute
tens_minute = minute-ones_minute
# Unfortunately we can't do the same trick we did with ones_minute here to get the word part
# Because we'll be getting tens[50] if our number is 52. But this can be easily solved
# We'll just divide tens_minute by 10 to get the number part of it
# So if tens_minute is 50, we'll get 5 by dividing that and tens[5]='fifty' so it will work out.
tens_minute_num = tens_minute//10
# You may find it odd that we use integer division here but the reason is that regular division will return a float
# And we can't use floats as indices.
tens_minute_writing = tens[tens_minute_num]
# Putting it all together
# Now we can simply return hour_writing, tens_minute_writing, ones_minute_writing
# But our problem here is with the English language. Because 15 is "fifteen" not ten five.
# We'll first make an if statement to check for this and fix our words accordingly.
if 10 < minute < 20:
# Make a list of our 'weird' words
weird = ['', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen']
# This list is also conveniently set up but it just needs a little work.
# Notice how with our new list, weird[1] = 'eleven'
# So we can just do weird[ones_minute] to get the word version of a number
weird_writing = weird[ones_minute]
#And now we'll return the full word part
return hour_writing+' '+weird_writing+' '+appendix
else:
# Now we'll return the regular. Note that if the minute isn't between 10 and 20 we haven't returned anything yet.
# return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
# But we must be aware that if tens_minute_writing or ones_minute_writing is '' then there will be too many spaces
# We can fix that with a nested if statement
if ones_minute_writing == '' and tens_minute_writing == '':
# This will only work when both of the writings are ''
return hour_writing+' '+tens_minute_writing+ones_minute_writing+appendix
elif (ones_minute_writing == '') and (tens_minute_writing != ''):
# This will work when ones_minute_writing is '' but tens_minute_writing isn't.
return hour_writing+' '+tens_minute_writing+' '+appendix
else:
return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix
Code in full w/o Comments
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def time2words(time_string):
time_list = time_string.split(':')
hour = int(time_list[0])
minute = int(time_list[1])
ones = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
tens = ['', 'ten', 'twenty', 'thirty', 'forty', 'fifty']
hours = ['twelve', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve']
hour_writing = hours[hour%12]
if hour == 24:
appendix = 'am'
elif hour == 12:
appendix = 'pm'
elif hour > 12:
appendix = 'pm'
else:
appendix = 'am'
ones_minute = minute%10
ones_minute_writing = ones[ones_minute]
tens_minute = minute-ones_minute
tens_minute_num = tens_minute//10
tens_minute_writing = tens[tens_minute_num]
if 10 < minute < 20:
weird = ['', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen']
weird_writing = weird[ones_minute]
return hour_writing+' '+weird_writing+' '+appendix
else:
if ones_minute_writing == '' and tens_minute_writing == '':
return hour_writing+' '+appendix
elif (ones_minute_writing == '') and (tens_minute_writing != ''):
return hour_writing+' '+tens_minute_writing+' '+appendix
else:
return hour_writing+' '+tens_minute_writing+' '+ones_minute_writing+' '+appendix