ValueError: incomplete format

The error ValueError: incomplete format occurs in the string that contains a percentage symbol (“%”) without any following format specifier characters.

The string format specifyer is used to dynamically replace the value in the string. The string uses percent (“%”) to specify the formats. The python interpreter throws “ValueError: incomplete format” error, if a string contains percent symbol without any format specifier character.

In python, a character is expected to follow the percentage (%) in the string to inform it how to represent the variable in the string. The “ValueError: incomplete format” error is thrown if the character is not found after the percentage symbol in the string.

Exception

The “ValueError: incomplete format” error will be shown as below if a character is not found after the percentage symbol.

Traceback (most recent call last):
  File "/Users/python/Desktop/test.py", line 4, in <module>
    print "The percentage is %" % x
ValueError: incomplete format
[Finished in 0.0s with exit code 1]

Root Cause

The percentage symbol (%) is used to specify the formater in the python strings. The character followed by the percentage indicates how to represent the value in the string. The reason for this issue is that the format specifier character is missing after the percentage symbol.

Solution 1

The percentage symbol represents for the format specifier in the python string. If the percentage symbol is not required in the string, remove it from the string. This will resolve the “ValueError: incomplete format” error.

Program

x = 5
print "The percentage is %s %" % x

Output

Traceback (most recent call last):
  File "/Users/python/Desktop/test.py", line 4, in <module>
    print "The percentage is %" % x
ValueError: incomplete format
[Finished in 0.0s with exit code 1]

Solution

x = 5
print "The percentage is %s" % x

Output

The percentage is 5
[Finished in 0.1s]

Solution 2

The percentage symbol is used for the format specifier in the python string. If the percentage symbol is required to be printed in the string, add another percentage symbol next to it in the string. This will resolve the “ValueError: incomplete format” error.

Program

x = 5
print "The percentage is %s %" % x

Output

Traceback (most recent call last):
  File "/Users/python/Desktop/test.py", line 4, in <module>
    print "The percentage is %" % x
ValueError: incomplete format
[Finished in 0.0s with exit code 1]

Solution

x = 5
print "The percentage is %s%%" % x

Output

The percentage is 5%
[Finished in 0.1s]

Solution 3

The percentage symbol represents for the format specifier in the python string. The character is expected to follow the percentage (percent) in the string to tell it how to represent the variable in the string. If the character is missing from the string, add the character after the percentage symbol.

Program

x = 5
y = 10
print "The percentage is %s %" % x

Output

Traceback (most recent call last):
  File "/Users/python/Desktop/test.py", line 4, in <module>
    print "The percentage is %" % x
ValueError: incomplete format
[Finished in 0.0s with exit code 1]

Solution

x = 5
y = 10
print "The percentage is %s %s" % (x, y)

Output

The percentage is 5 10
[Finished in 0.0s]

Solution 4

Python supports the new way to represent the format specifier in the string.
The curly brace is used to represent the format specifier. To use a new format, change the percentage symbol from the string to the new curly brace. This resolves the percentage issue as well as the error “ValueError: incomplete format”

Program

x = 5
y = 10
print "The percentage is %s %" % x

Output

Traceback (most recent call last):
  File "/Users/python/Desktop/test.py", line 4, in <module>
    print "The percentage is %" % x
ValueError: incomplete format
[Finished in 0.0s with exit code 1]

Solution

x = 5
y = 10
print "The percentage is {0} {1}".format(x, y)

Output

The percentage is 5 10
[Finished in 0.0s]