CODEWITHSUNDEEP
python
sdbbs
sdbbs

Reputation: 5394

Why does pprint show a different class from print?

Consider this example, adapted from Correct, "full length" left-right arrows in Matplotlib?:

import matplotlib.pyplot as plt
import pprint

fig = plt.figure()
ax = fig.add_subplot()
ax.plot([0],[0])
ax.grid()
ax.set_xlim([0,10])
ax.set_ylim([0,10])
ret = ax.annotate("", (2, 1), (4, 1), arrowprops={'arrowstyle':'<->', 'shrinkA': 0, 'shrinkB': 0})
print("print ret: {}".format(ret))            # print ret: Annotation(2, 1, '')
pprint.pprint("print ret: {}".format(ret))    # "print ret: Annotation(2, 1, '')"
print(ret)                                    # Annotation(2, 1, '')
pprint.pprint(ret)                            # Text(4, 1, '')
plt.show()

So, pretty much all printouts of the ret variable consider it as of class Annotation - except if I put ret directly in pprint, in which case I get a different class, Text. I find that a bit inconsistent, because I'd expect every printout of the variable to result with the same class name.

Is this expected behavior of pprint - and if so, why does it happen?

This was on MINGW64 python:

$ python3 --version
Python 3.9.7

Upvotes: 0

Views: 73

Answers (1)

buran
buran

Reputation: 14233

When you use string formatting, implicit string conversion is applied. class Annotation has __str__() method defined, but no __repr__().

pprint() prints the formatted representation of object (the docs), so it try to use Annotation.__repr__(), but it is not defined so it falls back to parent's Text.__repr__() (note that Annotation inherits from Text)

You can compare the result of str(ret) and repr(ret).

Upvotes: 1

Related Questions