$MaxLengthIntStringConversion

Python 3.11 Integer string conversion length limitation


$MaxLengthIntStringConversion

A positive system integer that fixes the largest size of the string that can appear when converting an Integer value into a String. When the string value is too large, then the middle of the integer contains an indication of the number of digits elided inside << >>.

If $MaxLengthIntStringConversion is set to 0, there is no bound. Aside from 0, 640 is the smallest value allowed.

The initial value can be set via environment variable DEFAULT_MAX_STR_DIGITS. If that is not set, the default value is 7000.


Although Mathics3 can represent integers of arbitrary size, when it formats the value for display, there can be nonlinear behavior in printing the decimal string or converting it to a String.

Python, in version 3.11 and up, puts a default limit on the size of the number of digits allows when converting a large integer into a string.

Show the default value of $MaxLengthIntStringConversion:

500! is a 1135-digit number:

We first set $MaxLengthIntStringConversion to the smallest value allowed, so that we can see the truncation of digits in the middle:

Note that setting $MaxLengthIntStringConversion has an effect only on Python 3.11 and later;
Pyston 2.x however ignores this.

Now when we print the string value of 500! and Pyston 2.x is not used, the middle digits are removed:

To see this easier, manipulate the result as String:

The <<501>> indicates that 501 digits have been omitted in the string conversion.

Other than 0, an Integer value less than 640 is not accepted:

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