I want to have a single assignment variable but make the assignment later (in a different block).
For example:
let n: int
try:
n = parseInt paramStr(1)
except ValueError:
quit "Expected Number
Is this impossible right now? If so, why?
Also what is the best alternative in this situation?
I considered this:
let n =
try:
parseInt paramStr(2)
except ValueError:
-1
if n == -1:
quit "Expected a number"
but doesn't look nice of course...
It is impossible given the current implementation, your alternative seems reasonable to me (or use a var with initial value of -1). Otherwise you can use the parseopt module to abstract the command line input verification logic.
You can do something like:
let n =
try:
var n: int
let processedChars = paramStr(1).parseInt(n)
if processedChars == 0:
quit "Expected number"
n
except ValueError:
quit "Parsed integer is out of the valid range"
Also note that parseInt doesn't return the parsed value, but rather the number of parsed characters.
Related
I am trying to create a function that would take a user inputted number and determine if the number is an integer or a floating-point depending on what the mode is set to. I am very new to python and learning the language and I am getting an invalid syntax error and I don't know what to do. So far I am making the integer tester first. Here is the code:
def getNumber(IntF, FloatA, Msg, rsp):
print("What would you like to do?")
print("Option A = Interger")
print("Option B = Floating Point")
Rsp = int(input("What number would like to test as an interger?"))
A = rsp
if rsp == "A":
while True:
try:
userInput = int(input("What number would like to test as an interger"))
except ValueError as ve:
print("Not an integer! Try again.")
continue
else:
return userInput
break
The problem with the code you shared is :
The syntax error you mentioned is probably because the except clause has to be at the same indentation level as try, and same for if and else of the same if/else clause. All the code in the function should be indented 1 level too. Python requires all this to identify blocks of code.
You don't need to give 4 arguments to the getNumber() function if you're not using them. This isn't really a problem, but you'll have to pass it some 4 values each time you call it (for example getNumber(1,2,3,4) etc...) to avoid missing argument errors; and these won't matter because you're not doing anything with the given values inside the function - so it's a little wasted effort. I rewrote it in the example below so that you aren't dealing with more variables than you need - it makes the code clearer/simpler.
You also don't need break after a return statement because the return will exit the enitre function block, including the loop.
Try this and see if it makes sense - I've changed a lot of the code :
def getNumber():
while True:
try:
userInput = int(input("What number would like to test as an integer ? "))
return userInput
except ValueError as ve:
print("Not an integer! Try again.")
continue
print("What would you like to do?")
print("Option A = Interger")
print("Option B = Floating Point")
chosen_option = input()
if chosen_option == 'A':
integer_received = getNumber()
print(integer_received, "was an int !")
else:
print("You did not choose 'A' or 'B'")
To determine whether a number is a float or integer, you can use this approach
float is nothing but the integer with floating-point(.).
to determine this we first need to convert it to string and find does it contain a point or not.
number = input("Enter a numbeer\n")
if number.find(".") == -1:
# find will return -1 when the value is not in string
print("it is integer")
else:
print("it is float")
beginner here so be kind.
This is my example code.
def iq_test(numbers): for i in numbers: if int(i) %2 != 0: return i
This bit of code always returns the invalid literal for base10... which is weird as when the mod operator is == 0, it doesn't return the error. Where am I going wrong?
I've tried .isdigit, tried to use a float instead but no joy.
You haven't stated what your requirement is, so I will guess that it is to "extract the first odd number from a string containing a mixture of numbers and letters".
You also wonder why i % 2 == 0 allows some specific test to work, but that might only be because the string being tested only contains even numbers.
Here is your function adjusted to answer that hypothetical question:
def iq_test(numbers):
for i in numbers:
if str(i).isdigit() and int(i) %2 != 0:
return i
Note the stringify requirement for testing each element of the string/list as integer.
So, my exercise ask me to get inputs from the user (integer) and break the process of getting numbers once the user types "done". Then the desired output should be:
Smallest number =
Largest number =
Problem is:
I set 2 variables smallest and largest this way:
smallest = None
largest = None
But when i try to compare the user input with theses variables i get an error " TypeError: '>' not supported between instances of 'int' and 'NoneType', I tried casting the string to int an still getting the same error.
Can someone help me? Thanks,
My code so far:
largest = None
Smallest = None
while True:
num = input("Enter a number: ")
if num == "done": break
try:
val = float(num)
except:
print("Invalid input")
continue
number = int(num)
if number > largest:
largest =number
king
When the first valid input comes, the variable number is an int while the variable largest is still None. You try to compare them with '>' operator, that's why the error is thrown.
You can set the initial value of largest/smallest as the first valid number.
I am having some issues with some code I wrote for this problem:
“Write a function namedd calc that will evaluate a simple arithmetic expression. The input to your program will be a string of the form:
operand1 operator operand2
where operand1 and operand2 are non-negative integers and operator is a single-character operator, which is either +, -, or *. You may assume that there is a space between each operand and the operator. You may further assume that the input is a valid mathemat- ical expression, i.e. your program is not responsible for the case where the user enters gibberish.
Your function will return an integer, such that the returned value is equal to the value produced by applying the given operation to the given operands.
Sample execution:
calc("5 + 10") # 15
“You may not use the split or eval functions in your solution.
Hint: the hard part here is breaking the input string into its three component. You may use the find and rfind functions to find the position of the first and last space, and then use the slice operator (that is, s[startindex:endindex]) to extract the relevant range of characters. Be careful of off-by-one errors in using the slice operator.
Hint: it’s best to test your code as you work. The first step should be to break the input string into its three components. Write a program that does that, have it print out the operator and the two operands on separate lines, and test it until you are convinced that it works. Then, modifying it to perform the desired mathematical operation should be straightforward. Test your program with several different inputs to make sure it works as you expect.”
Here is my code:
def calc(exp):
operand1 = int(exp[:1])
operand2 = int(exp[4:6])
operator = exp[2:3]
if(operator == "+"):
addition = operand1+operand2
return addition
if(operator == "-"):
subtraction = operand1-operand2
return subtraction
if(operator == "*"):
multiplication = operand1*operand2
return multiplication
print(calc("5 + 10"))
print(calc("4 - 8"))
print(calc("4 * 3"))
My code does not fully meet the criteria of this question. It only works for single digit numbers. How can I make my code work for any number?
Like:
“504 + 507”
”5678 + 76890”
and so on?
Thank you. Any help is appreciated.
As the hint says, get the position of the first and last space of the expression, use it to extract the operand and the operators, and then evaluate accordingly.
def calc(exp):
#Get the position for first space with find
low_idx = exp.find(' ')
#Get the position for last space with rfind
high_idx = exp.rfind(' ')
#Extract operators and operand with slice, converting operands to int
operand1 = int(exp[0:low_idx])
operator = exp[low_idx+1:high_idx]
operand2 = int(exp[high_idx:])
result = 0
#Evaluate based on operator
if operator == '+':
result = operand1 + operand2
elif operator == '-':
result = operand1 - operand2
elif operator == '*':
result = operand1 * operand2
return result
print(calc("5 + 10"))
print(calc("4 - 8"))
print(calc("4 * 3"))
print(calc("504 + 507"))
print(calc("5678 + 76890"))
#15
#-4
#12
#1011
#82568
The answer is in the specification:
You may use the find and rfind functions to find the position of the first and last space, and then use the slice operator (that is, s[startindex:endindex]) to extract the relevant range of characters.
find and rfind are methods of string objects.
You could split it into three components using this code: (note: this doesn't use split or eval)
def splitExpression(e):
numbers = ["1","2","3","4","5","6","7","8","9","0"] # list of all numbers
operations = ["+","-","*","/"] # list of all operations
output = [] # output components
currentlyParsing = "number" # the component we're currently parsing
buildstring = "" # temporary variable
for c in e:
if c == " ":
continue # ignore whitespace
if currentlyParsing == "number": # we are currently parsing a number
if c in numbers:
buildstring += c # this is a number, continue
elif c in operations:
output.append(buildstring) # this component has reached it's end
buildstring = c
currentlyParsing = "operation" # we are expecting an operation now
else:
pass # unknown symbol!
elif currentlyParsing == "operation": # we are currently parsing an operation
if c in operations:
buildstring += c # this is an operation, continue
elif c in numbers:
output.append(buildstring) # this component has reached it's end
buildstring = c
currentlyParsing = "number" # we are expecting a number now
else:
pass # unknown symbol!
if buildstring: # anything left in the buffer?
output.append(buildstring)
buildstring = ""
return output
Usage: splitExpression("281*14") returns ["281","*","14"]
This function also accepts spaces between numbers and operations
You can simply take the string and use the split method for the string object, which will return a list of strings based on some separator.
For example:
stringList = "504 + 507".split(" ")
stringList will now be a list such as ["504", "+", "507"] due to the separator " " which is a whitespace. Then just use stringList[1] with your conditionals to solve the problem. Additionally, you can use int(stringList[0]) and int(stringList[2]) to convert the strings to int objects.
EDIT:
Now I realized that your problem said to use find() instead of split(). Simply use the logic above but instead find(" ") the first whitespace. You will then need to find the second whitespace by slicing past the first whitespace using the two additional arguments available for find().
You need to split the string out instead of hard coding the positions of the indexes.
When coding you want to try to make your code as dynamic as possible, that generally means not hard coding stuff that could be a variable or in this case could be grabbed from the spaces.
Also in the if statements I modified them to elif as it is all one contained statement and thus should be grouped.
def calc(exp):
vals = exp.split(' ')
operand1 = int(vals[0])
operand2 = int(vals[2])
operator = vals[1]
if operator == '+':
return operand1+operand2
elif operator == '-':
return operand1-operand2
else:
return operand1*operand2
I am creating a cipher script in python without any modules but I have come accross a problem that i cant solve. When I am comparing msg[3] which has the value (space) it should be equal to bet[26] which is also a space. If i compare msg[3] with bet[26] in the shell...
>>>msg[3] == bet[26]
True
The output is True. However when i run the program and output the value of enmsg there is no value 26 where the value 26 should be.
enmsg = []
msg = "try harder"
bet = "abcdefghijklmnopqrstuvwxyz "
for x in range(0, len(msg)):
for i in range(0, 26):
if msg[x] == bet[i]:
print(msg[x])
enmsg.append(i)
You should get out of the habit of iterating over a range of indices and then looking up the value at the index. Instead iterate directly over your iterables, using enumerate when necessary.
enmsg = []
msg = "try harder"
bet = "abcdefghijklmnopqrstuvwxyz "
for msg_char in msg:
for index, bet_char in enumerate(bet):
if msg_char == bet_char:
print(msg_char)
enmsg.append(index)
Your second loop iterations are too short so it is not reaching the space symbol.
Try with this:
enmsg = []
msg = "try harder"
bet = "abcdefghijklmnopqrstuvwxyz "
for x in range(0, len(msg)):
for i in range(len(bet)):
if msg[x] == bet[i]:
print(msg[x])
enmsg.append(i)
The upper bound of range is not inclusive; you'll need to extend this by one to actually check the 26th index of the string. Better yet, iterate up through len(bet) as you did for len(msg) for the outer loop.