# Cert-tools error: AttributeError: 'str' object has no attribute 'isoformat'. Did you mean: 'format'?

**URL:** <https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222>\
**Category:** Uncategorized\
**Created:** [June 16, 2022, 10:40pm UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222 "2022-06-16T22:40:09Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![jhdezctza](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@jhdezctza](https://community.blockcerts.org/u/jhdezctza)\
**Post date:** [June 16, 2022, 10:40pm UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/1 "2022-06-16T22:40:09Z")

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help me please: cert-tools error

 ![image](https://us1.discourse-cdn.com/flex016/uploads/blockcerts/original/1X/c5c340f802e07031d36d684453597577578c7245.png)

AttributeError: ‘str’ object has no attribute ‘isoformat’. Did you mean: ‘format’?

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**Author:** ![lemoustachiste](https://avatars.discourse-cdn.com/v4/letter/l/7c8e57/32.png) [@lemoustachiste](https://community.blockcerts.org/u/lemoustachiste)\
**Post date:** [June 27, 2022, 7:22pm UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/2 "2022-06-27T19:22:18Z")

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which python version are you running?

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**Author:** ![jhdezctza](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@jhdezctza](https://community.blockcerts.org/u/jhdezctza)\
**Post date:** [June 28, 2022, 10:04pm UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/3 "2022-06-28T22:04:56Z")

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I use the version Python 3.10 😢

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**Author:** ![lemoustachiste](https://avatars.discourse-cdn.com/v4/letter/l/7c8e57/32.png) [@lemoustachiste](https://community.blockcerts.org/u/lemoustachiste)\
**Post date:** [June 29, 2022, 12:15am UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/4 "2022-06-29T00:15:42Z")

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could you try and use 3.8?  
This one is supported, 3.10, not sure.

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<div class="post-metadata">

**Author:** ![jhdezctza](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@jhdezctza](https://community.blockcerts.org/u/jhdezctza)\
**Post date:** [June 29, 2022, 12:48am UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/5 "2022-06-29T00:48:30Z")

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I’ve already tried and it doesn’t work

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<div class="post-metadata">

**Author:** ![lemoustachiste](https://avatars.discourse-cdn.com/v4/letter/l/7c8e57/32.png) [@lemoustachiste](https://community.blockcerts.org/u/lemoustachiste)\
**Post date:** [June 30, 2022, 1:18pm UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/6 "2022-06-30T13:18:35Z")

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I vaguely remember someone opening a PR along these lines, a few years back, I thought on cert-issuer but I wasn’t able to find it.

I suppose you can try to follow the error message and see what it does, and potentially open a PR?

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**Author:** ![mary.tellez](https://sea2.discourse-cdn.com/flex016/user_avatar/community.blockcerts.org/mary.tellez/32/856_2.png) [@mary.tellez](https://community.blockcerts.org/u/mary.tellez)\
**Post date:** [July 15, 2022, 12:24am UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/7 "2022-07-15T00:24:58Z")

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Hi, i´m resolve this replace return ret.isoformat() with return ret and this works for me.

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**Author:** ![x41lakazam](https://sea2.discourse-cdn.com/flex016/user_avatar/community.blockcerts.org/x41lakazam/32/889_2.png) [@x41lakazam](https://community.blockcerts.org/u/x41lakazam)\
**Post date:** [October 29, 2023, 3:36pm UTC](https://community.blockcerts.org/t/cert-tools-error-attributeerror-str-object-has-no-attribute-isoformat-did-you-mean-format/3222/8 "2023-10-29T15:36:53Z")

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Hey, the issue is a hard-coded (and pretty obvious) bug, and does not depend on python version.  
Please merge [pull request cert-tools#55](https://github.com/blockchain-certificates/cert-tools/pull/55) to solve it.