CODEWITHSUNDEEP
pythonnumpy
makhlaghi
makhlaghi

Reputation: 3986

ValueError: Unknown format code 'g' for object of type 'str'

I am new to Python and I am trying to write a simple print function but I am getting a strange error. This is my code:

#! /usr/bin/env python3.2
import numpy as np

a=np.arange(1,10,1)
print(a)
for i in a:
    print(i)
    print(type(i))
    print("{0:<12g}".format(i))

The output is: 

[1 2 3 4 5 6 7 8 9]
1
<class 'numpy.int64'>
Traceback (most recent call last):
  File "./test.py", line 9, in <module>
    print("{0:<12g}".format(i))
ValueError: Unknown format code 'g' for object of type 'str'

Why does print take the "numpy.int64" as a string? I have to add that it works perfectly for a normal list: (e.g. [1,2,3,4]) I would be most grateful to any ideas on this issue, thanks ;-).

Upvotes: 2

Views: 14591

Answers (3)

Loris Constantin
Loris Constantin

Reputation: 43

If you stumble upon this error while trying to use seaborn.heatmap with annotations such as:

import seaborn as sns
import numpy as np

data = pd.DataFrame(np.random.rand(3,4))
annot = np.where(data > 0, 'Yes', 'No')
ax = sns.heatmap(data, annot=annot)

ValueError: Unknown format code 'g' for object of type 'numpy.str_'

You can make it work by adding fmt='' as argument to sns.heatmap such as:

ax = sns.heatmap(data, annot=annot, fmt='')

It should do the trick.

Upvotes: 1

Burhan Khalid
Burhan Khalid

Reputation: 174624

This is a known bug and should be fixed in version 2.0. In the interim, you can use the old syntax %f that works.

Upvotes: 2

TankorSmash
TankorSmash

Reputation: 12747

Someone will be able to give you a more in-depth answer, but what I think is happening here is that you're using "{0:<12g}".format(i) which uses special formatting. If you'd try "\{{0}:<12g\}".format(i) you'd probably get better results. Using the slashes there escapes the {}'s which is what is giving you the error.

Upvotes: 0

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