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ArcGIS Pro 2.8.4: A python expression fails to perform on “field calculator”,

JamalNUMAN

I couldn’t figure out why the python expression below fails to perform on “field calculator

!A! + "/"+ !B!

This expression is supposed to combine the field A and field B in field C. The first value in the C table when computed is assumed to be 33 / 1

What could be the issue here?

The gdb file is attached

M.gdb.zip

GauravJobanputra_0-1722389166970.png

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Accepted answers

Luke_Pinner

Again, use string formatting

f"{!A!:.0f} / {!B!:.0f}"

"{:.0f} / {:.0f}".format(!A!, !B!)

"%.0f / %.0f" % (!A!, !B!)

All comments

Luke_Pinner

The error message is telling you that you can't add a string to a number. The "+" operator is for adding numbers or concatenating strings, not adding or concatenating strings to numbers.

Use string formatting instead:

C = f"{!A!} / {!B!}"

# or 
C = "{} / {}".format(!A!, !B!)

# or
C = "%s / %s" % (!A!, !B!)

JohannesLindner

A and B are floats, "/" is a string.

In Python, addition between float and str isn't defined, so the Field Calculator doesn't know what to do.

You have to convert the floats to strings using one of these methods:

# explicitly cast the floats to strings
str(!A!) + "/" + str(!B!)

# implicitly cast to string with str.format()
"{}/{}".format(!A!, !B!)

# implicitly cast to string with format string
f"{!A!}/{!B!}"

JamalNUMAN

The expression (str(!A!) + "/" + str(!B!)) adds one decimal number for each number.

How to eliminate this decimal number?

JoshuaBixby

You are making it harder than it has to be. Just don't wrap your Python division character in a string. For example:

!A! / !B!

Luke_Pinner

@JoshuaBixby then will the result be the division of the two numbers (not what OP wants) instead of a string with the two numbers separated by a forward slash (what the OP wants)?

Luke_Pinner

Again, use string formatting

f"{!A!:.0f} / {!B!:.0f}"

"{:.0f} / {:.0f}".format(!A!, !B!)

"%.0f / %.0f" % (!A!, !B!)

JamalNUMAN

Thank you for the help. It works fine

JoshuaBixby

@Luke_Pinner, I was too quick skimming over the question, thanks for pointing out the real question.

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