Related
I got this error from my code:
ValueError: invalid literal for int() with base 10: ''.
What does it mean? Why does it occur, and how can I fix it?
The error message means that the string provided to int could not be parsed as an integer. The part at the end, after the :, shows the string that was provided.
In the case described in the question, the input was an empty string, written as ''.
Here is another example - a string that represents a floating-point value cannot be converted directly with int:
>>> int('55063.000000')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '55063.000000'
Instead, convert to float first:
>>> int(float('55063.000000'))
55063
See：https://www.geeksforgeeks.org/python-int-function/
The following work fine in Python:
>>> int('5') # passing the string representation of an integer to `int`
5
>>> float('5.0') # passing the string representation of a float to `float`
5.0
>>> float('5') # passing the string representation of an integer to `float`
5.0
>>> int(5.0) # passing a float to `int`
5
>>> float(5) # passing an integer to `float`
5.0
However, passing the string representation of a float, or any other string that does not represent an integer (including, for example, an empty string like '') will cause a ValueError:
>>> int('')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''
>>> int('5.0')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '5.0'
To convert the string representation of a floating-point number to integer, it will work to convert to a float first, then to an integer (as explained in #katyhuff's comment on the question):
>>> int(float('5.0'))
5
int cannot convert an empty string to an integer. If the input string could be empty, consider either checking for this case:
if data:
as_int = int(data)
else:
# do something else
or using exception handling:
try:
as_int = int(data)
except ValueError:
# do something else
Python will convert the number to a float. Simply calling float first then converting that to an int will work:
output = int(float(input))
This error occurs when trying to convert an empty string to an integer:
>>> int(5)
5
>>> int('5')
5
>>> int('')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''
The reason is that you are getting an empty string or a string as an argument into int. Check if it is empty or it contains alpha characters. If it contains characters, then simply ignore that part.
Given floatInString = '5.0', that value can be converted to int like so:
floatInInt = int(float(floatInString))
You've got a problem with this line:
while file_to_read != " ":
This does not find an empty string. It finds a string consisting of one space. Presumably this is not what you are looking for.
Listen to everyone else's advice. This is not very idiomatic python code, and would be much clearer if you iterate over the file directly, but I think this problem is worth noting as well.
My simple workaround to this problem was wrap my code in an if statement, taking advantage of the fact that an empty string is not "truthy":
Given either of these two inputs:
input_string = "" # works with an empty string
input_string = "25" # or a number inside a string
You can safely handle a blank string using this check:
if input_string:
number = int(input_string)
else:
number = None # (or number = 0 if you prefer)
print(number)
I recently came across a case where none of these answers worked. I encountered CSV data where there were null bytes mixed in with the data, and those null bytes did not get stripped. So, my numeric string, after stripping, consisted of bytes like this:
\x00\x31\x00\x0d\x00
To counter this, I did:
countStr = fields[3].replace('\x00', '').strip()
count = int(countStr)
...where fields is a list of csv values resulting from splitting the line.
This could also happen when you have to map space separated integers to a list but you enter the integers line by line using the .input().
Like for example I was solving this problem on HackerRank Bon-Appetit, and the got the following error while compiling
So instead of giving input to the program line by line try to map the space separated integers into a list using the map() method.
your answer is throwing errors because of this line
readings = int(readings)
Here you are trying to convert a string into int type which is not base-10. you can convert a string into int only if it is base-10 otherwise it will throw ValueError, stating invalid literal for int() with base 10.
This seems like readings is sometimes an empty string and obviously an error crops up.
You can add an extra check to your while loop before the int(readings) command like:
while readings != 0 or readings != '':
readings = int(readings)
I am creating a program that reads a
file and if the first line of the file
is not blank, it reads the next four
lines. Calculations are performed on
those lines and then the next line is
read.
Something like this should work:
for line in infile:
next_lines = []
if line.strip():
for i in xrange(4):
try:
next_lines.append(infile.next())
except StopIteration:
break
# Do your calculation with "4 lines" here
Another answer in case all of the above solutions are not working for you.
My original error was similar to OP: ValueError: invalid literal for int() with base 10: '52,002'
I then tried the accepted answer and got this error: ValueError: could not convert string to float: '52,002' --this was when I tried the int(float(variable_name))
My solution is to convert the string to a float and leave it there. I just needed to check to see if the string was a numeric value so I can handle it correctly.
try:
float(variable_name)
except ValueError:
print("The value you entered was not a number, please enter a different number")
I have a string that looks identical to a list, let's say:
'[万福广场西,凰花苑]'
I would like to convert it into something like this:
['万福广场西','凰花苑']
I used eval() and ast.literal_eval() but got error as following:
y=eval('[万福广场西,凰花苑]')
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-117-0aadbead218c> in <module>()
----> 1 y=eval('[万福广场西,凰花苑]')
<string> in <module>()
NameError: name '万福广场西' is not defined
when using ast.literal_eval(), I got this error ValueError: malformed node or string: <_ast.Name object at 0x000002A67FFA5CC0>
Try Something like
my_list = '[万福广场西,凰花苑]'[1:-1].split(",")
It will return you an list -- ['万福广场西', '凰花苑']
You can check it as -- type(my_list) #<class 'list'>
Use strip and split
>>> '[万福广场西,凰花苑]'.strip('[]').split(",")
['万福广场西', '凰花苑']
eval() will consider the given string as python code and return the result. So as per your string, the python code will something like this [万福广场西,凰花苑] which means two variable 万福广场西 and 凰花苑 are in a list.
If you want it to be evaluated as a list of strings you need to bound both strings with double quotes (") such as
'["万福广场西","凰花苑"]'.
When you subject this string to eval(), the output would be,
['万福广场西', '凰花苑']
If you want this to happen dynamically, you need to use split and join functions like,
''.join(list('[万福广场西,凰花苑]')[1:-1]).split(',')
which first makes the list of strings given by
list('[万福广场西,凰花苑]')[1:-1] # O/P ['万', '福', '广', '场', '西', ',', '凰', '花', '苑']
then joins all the strings as
''.join(['万', '福', '广', '场', '西', ',', '凰', '花', '苑']) # O/P 万福广场西,凰花苑
and splits the string by comma (,) to create your desired output.
'万福广场西,凰花苑'.split(',') # O/P ['万福广场西', '凰花苑']
Hope you have got what you were searching for. Feel free to comment in case of any clarifications required.
The content of your string isn't actually a valid list of literals because the literals are lacking the necessary quotes, so you can't parse it with eval() or ast.literal_eval().
Instead, you can use regular expression to parse the string into a list:
import re
print(re.findall(r'[^\[\],]+', '[万福广场西,凰花苑]'))
This outputs:
['万福广场西', '凰花苑']
I've been having trouble getting a specific print in Python 3.4
Input:
str=input("Input Here!!!:")
num = len(str)
x = num
print (((str))*x)
but I'm looking for an output that prints str x times, without using a loop.
for example if I enter:
Input Here!!!: Hello
I would get:
>>>Hello
>>>Hello
>>>Hello
>>>Hello
>>>Hello
You need to add a newline if you want the output on different lines:
In [10]: n = 5
In [11]: s = "hello"
In [12]: print((s+"\n")* n)
hello
hello
hello
hello
hello
It is not possible to get the output as if each string were the output of a new command. The closest to your expected output will be the code above.
You should never use built-in keywords, types for variable names. str is a built in type like list, int etc. Next time you would try to use it, will give you errors.
Ex -
>>> str = 'apple'
Now let's try to build a simple list of no.s as string.
>>> [ str(i) for i in range(4)]
Traceback (most recent call last):
File "<pyshell#298>", line 1, in <module>
[ str(i) for i in range(4)]
TypeError: 'str' object is not callable
Since we have already replaced our str with a string. It can't be called.
So let's use 's' instead of 'str'
s=input("Input Here!!!:")
print ( s * len(s) )
If you want output in different lines
print ( (s+"\n")* len(s) )
I don't know what exactly do you want to achieve. We can always replicate looping with a recursive function.
def input(s):
print(s)
def pseudo_for(n, my_func, *args):
if n==0:
return
else:
'''
Write function or expression to be repeated
'''
my_func(*args)
pseudo_for(n-1, my_func, *args)
pseudo_for(5, input, "Hello")
You can use join with a list comprehension:
>>> s='string'
>>> print('\n'.join([s for i in range(5)]))
string
string
string
string
string
Technically a list comprehension is a 'loop' I suppose, but you have not made clear what you mean by 'without using a loop'
You can also use string formatting in Python:
>>> fmt='{0}\n'*5
>>> fmt
'{0}\n{0}\n{0}\n{0}\n{0}\n'
>>> print(fmt.format('hello'))
hello
hello
hello
hello
hello
But that will have an extra \n at the end (as will anything using *n)
As Tim points out in comments:
>>> print('\n'.join([s]*5))
string
string
string
string
string
Is probably the best of all...
How to make word inputs in Python
I want to be able to have the computer to ask a question to the user like
test = int(input('This only takes a number as an answer'))
I want to be able to have 'test' not be a number, rather a word, or letter.
Just remove the int call! That is what makes the statement accept integer numbers only.
I.e, use:
test = input('This takes any string as an answer')
Remove the type cast to int
test = input('This only takes a word as an answer :')
A demo
>>> test = input('This only takes a word as an answer :')
This only takes a word as an answer :word
>>> test
'word'
Note - From the docs
The function then reads a line from input, converts it to a string (stripping a trailing newline), and returns that
Therefore input automatically converts it to a str and there is no need of any explicit cast.
This should work:
test = str(input('This only takes a string as an answer: '))
BUT
Because Python works with String by default, actually you don't need any casting like int or str
Also, if you were using version prior to 3.x, it would be raw_input instead of input. Since your solution seem to have been accepting input, I can be safe assuming that your Python is OK.
test = input('This only takes a string as an answer')
test = input("This only takes a number as an answer")
test = raw_input("This only takes a number as an answer")
Either one should work
If you are using python 2.7, just use raw_input function.
test = raw_input('This only takes a string as an answer: ')
I.e.:
>>> test = raw_input('This only takes a string as an answer: ')
This only takes a string as an answer: 2.5
>>> type (test)
<type 'str'>
If you use input, you can have only a number:
Right input:
>>> test = input('This only takes a number as an answer: ')
This only takes a string as an answer: 2.5
>>> type (test)
<type 'float'>
Wrong input:
>>> test = input('This only takes a number as an answer: ')
This only takes a number as an answer: word
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
NameError: name 'word' is not defined
I got this error from my code:
ValueError: invalid literal for int() with base 10: ''.
What does it mean? Why does it occur, and how can I fix it?
The error message means that the string provided to int could not be parsed as an integer. The part at the end, after the :, shows the string that was provided.
In the case described in the question, the input was an empty string, written as ''.
Here is another example - a string that represents a floating-point value cannot be converted directly with int:
>>> int('55063.000000')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '55063.000000'
Instead, convert to float first:
>>> int(float('55063.000000'))
55063
See：https://www.geeksforgeeks.org/python-int-function/
The following work fine in Python:
>>> int('5') # passing the string representation of an integer to `int`
5
>>> float('5.0') # passing the string representation of a float to `float`
5.0
>>> float('5') # passing the string representation of an integer to `float`
5.0
>>> int(5.0) # passing a float to `int`
5
>>> float(5) # passing an integer to `float`
5.0
However, passing the string representation of a float, or any other string that does not represent an integer (including, for example, an empty string like '') will cause a ValueError:
>>> int('')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''
>>> int('5.0')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '5.0'
To convert the string representation of a floating-point number to integer, it will work to convert to a float first, then to an integer (as explained in #katyhuff's comment on the question):
>>> int(float('5.0'))
5
int cannot convert an empty string to an integer. If the input string could be empty, consider either checking for this case:
if data:
as_int = int(data)
else:
# do something else
or using exception handling:
try:
as_int = int(data)
except ValueError:
# do something else
Python will convert the number to a float. Simply calling float first then converting that to an int will work:
output = int(float(input))
This error occurs when trying to convert an empty string to an integer:
>>> int(5)
5
>>> int('5')
5
>>> int('')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''
The reason is that you are getting an empty string or a string as an argument into int. Check if it is empty or it contains alpha characters. If it contains characters, then simply ignore that part.
Given floatInString = '5.0', that value can be converted to int like so:
floatInInt = int(float(floatInString))
You've got a problem with this line:
while file_to_read != " ":
This does not find an empty string. It finds a string consisting of one space. Presumably this is not what you are looking for.
Listen to everyone else's advice. This is not very idiomatic python code, and would be much clearer if you iterate over the file directly, but I think this problem is worth noting as well.
My simple workaround to this problem was wrap my code in an if statement, taking advantage of the fact that an empty string is not "truthy":
Given either of these two inputs:
input_string = "" # works with an empty string
input_string = "25" # or a number inside a string
You can safely handle a blank string using this check:
if input_string:
number = int(input_string)
else:
number = None # (or number = 0 if you prefer)
print(number)
I recently came across a case where none of these answers worked. I encountered CSV data where there were null bytes mixed in with the data, and those null bytes did not get stripped. So, my numeric string, after stripping, consisted of bytes like this:
\x00\x31\x00\x0d\x00
To counter this, I did:
countStr = fields[3].replace('\x00', '').strip()
count = int(countStr)
...where fields is a list of csv values resulting from splitting the line.
This could also happen when you have to map space separated integers to a list but you enter the integers line by line using the .input().
Like for example I was solving this problem on HackerRank Bon-Appetit, and the got the following error while compiling
So instead of giving input to the program line by line try to map the space separated integers into a list using the map() method.
your answer is throwing errors because of this line
readings = int(readings)
Here you are trying to convert a string into int type which is not base-10. you can convert a string into int only if it is base-10 otherwise it will throw ValueError, stating invalid literal for int() with base 10.
This seems like readings is sometimes an empty string and obviously an error crops up.
You can add an extra check to your while loop before the int(readings) command like:
while readings != 0 or readings != '':
readings = int(readings)
I am creating a program that reads a
file and if the first line of the file
is not blank, it reads the next four
lines. Calculations are performed on
those lines and then the next line is
read.
Something like this should work:
for line in infile:
next_lines = []
if line.strip():
for i in xrange(4):
try:
next_lines.append(infile.next())
except StopIteration:
break
# Do your calculation with "4 lines" here
Another answer in case all of the above solutions are not working for you.
My original error was similar to OP: ValueError: invalid literal for int() with base 10: '52,002'
I then tried the accepted answer and got this error: ValueError: could not convert string to float: '52,002' --this was when I tried the int(float(variable_name))
My solution is to convert the string to a float and leave it there. I just needed to check to see if the string was a numeric value so I can handle it correctly.
try:
float(variable_name)
except ValueError:
print("The value you entered was not a number, please enter a different number")