ValueError and TypeError in python
Question:
I can’t completely understand the difference between Type and Value error in Python3x.
Why do we get a ValueError when I try float(‘string’) instead of TypeError? shouldn’t this give also a TypeError because I am passing a variable of type ‘str’ to be converted into float?
In [169]: float('string')
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-169-f894e176bff2> in <module>()
----> 1 float('string')
ValueError: could not convert string to float: 'string'
Answers:
A Value error is
Raised when a built-in operation or function receives an argument that has the right type but an inappropriate value
the float function can take a string, ie float('5'), it’s just that the value 'string' in float('string') is an inappropriate (non-convertible) string
On the other hand,
Passing arguments of the wrong type (e.g. passing a list when an int is expected) should result in a TypeError
so you would get a TypeError if you tried float(['5']) because a list can never be converted into a float.
ValueError a function is called on a value of the correct type, but with an inappropriate value
TypeError : a function is called on a value of an inappropriate type
Just would like to add one more point to David’s answer.
TypeError can also occur, when we pass incorrect no of arguments to a function.
eg:
def hello(int x,int y):
pass
hello(12)
This also gives you TypeError:
hello() missing 1 required positional argument: ‘y’
They are well explained in
Python Documentation.
I would add examples for both of them:
TypeError:
10 + 'a'
ValueError:
int("hello")
ValueError and TypeError have very subtle differences
float('Dog') # Gives you an ValueError
The above statement gives you a ValueError, it may sound a little confusing, but now you realize that it makes sense.
The float function can accept a number or a string whose content is numeric as an argument.
Pay attention that I said that it accepts the string if it is a number, otherwise if the argument has a string of characters like dog, the type of argument that the float function receives is correct because it still received a string but the value it received is an inappropriate value for the float function.
According to the above, if an operation or function is given an argument whose type is correct, but the value inside that argument is inappropriate, TypeError will occur.The following example shows that an argument whose type is wrong causes a TypeError
var_ = [1, 2, 3] # Create a iterable
float(var_)
Note that the float function can take a string or a number, but the value inside the variable is an iterable, which does not match the type that the float function takes, so a TypeError is received due to the inappropriate type.
Python documentation about the float function
I can’t completely understand the difference between Type and Value error in Python3x.
Why do we get a ValueError when I try float(‘string’) instead of TypeError? shouldn’t this give also a TypeError because I am passing a variable of type ‘str’ to be converted into float?
In [169]: float('string')
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-169-f894e176bff2> in <module>()
----> 1 float('string')
ValueError: could not convert string to float: 'string'
A Value error is
Raised when a built-in operation or function receives an argument that has the right type but an inappropriate value
the float function can take a string, ie float('5'), it’s just that the value 'string' in float('string') is an inappropriate (non-convertible) string
On the other hand,
Passing arguments of the wrong type (e.g. passing a list when an int is expected) should result in a TypeError
so you would get a TypeError if you tried float(['5']) because a list can never be converted into a float.
ValueError a function is called on a value of the correct type, but with an inappropriate value
TypeError : a function is called on a value of an inappropriate type
Just would like to add one more point to David’s answer.
TypeError can also occur, when we pass incorrect no of arguments to a function.
eg:
def hello(int x,int y):
pass
hello(12)
This also gives you TypeError:
hello() missing 1 required positional argument: ‘y’
They are well explained in
Python Documentation.
I would add examples for both of them:
TypeError:
10 + 'a'
ValueError:
int("hello")
ValueError and TypeError have very subtle differences
float('Dog') # Gives you an ValueError
The above statement gives you a ValueError, it may sound a little confusing, but now you realize that it makes sense.
The float function can accept a number or a string whose content is numeric as an argument.
Pay attention that I said that it accepts the string if it is a number, otherwise if the argument has a string of characters like dog, the type of argument that the float function receives is correct because it still received a string but the value it received is an inappropriate value for the float function.
According to the above, if an operation or function is given an argument whose type is correct, but the value inside that argument is inappropriate, TypeError will occur.The following example shows that an argument whose type is wrong causes a TypeError
var_ = [1, 2, 3] # Create a iterable
float(var_)
Note that the float function can take a string or a number, but the value inside the variable is an iterable, which does not match the type that the float function takes, so a TypeError is received due to the inappropriate type.
Python documentation about the float function