**UPDATE**: Most (if not all) of these bugs have been fixed since I started using Pyjamas. This is here mainly for reference.

Pyjamas has a very useful migration guide which summarizes the current issues/differences between JS and Python that the developers did not yet resolve. It’s a very useful read for anyone using Pyjamas, both with JS and Python background and a must-read for anyone wishing to make an app that works both in browser and in Pyjamas-Desktop. I did find a few issues, however, that weren’t yet documented. So I decided to post them here, including the work-arounds.

## Importing radians function from math

### Description:

For some reason, the following code will cause an ImportError in JS:

`import math`

math.radians(degs)

However, doing the same with `math.pi`

, `math.sin`

, `math.cos`

, `math.sqrt`

works fine

### Solution:

Either use the following:

`from math import radians`

radians(degs)

Or:

`from math import pi`

degs*pi/180

## Concatenating two strings using +

### Description:

The following works fine in Python and Pyjamas-Desktop, but throws an exception (that Pyjamas catches, and gives “inform the webmaster” error):

`b="jamas"`

a="py"+b

Ironically, passing the same into a function as an argument works fine in both:

`b="jamas"`

fun("py"+b)

### Solution:

The following alternative works in both:

`b="jamas"`

a=''.join(["py",b])

Alternatively, if you want a cleaner-looking concatenation:

`def strcat(*args):`

return ''.join(args) b="jamas"

a=strcat("py",b)

## Different modulo implementation

### Description:

When performing the modulo command, Python uses the sign of the divisor for the result. JS, however uses the sign of the dividend. The following code in Pyjamas-Desktop will set a to 0.6, while in JS/browser it will set it to -0.4:

`a=(-0.4)%1`

### Solution:

So far, my solution is to do the following:

`a=dividend%divisor if a<0:`

a+=divisor

I also tried using `math.fmod()`

instead, but ran into the same ImportError issue as described above for radians, unfortunately using the work-around described above only works for `radians()`

. For `fmod()`

Pyjamas will throw “*$module.math.fmod is not a function*” exception