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cbook.is_sequence_of_strings knows string objects #4358

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merged 1 commit into from Apr 30, 2015
Merged

cbook.is_sequence_of_strings knows string objects #4358

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18 changes: 18 additions & 0 deletions doc/users/whats_new/cbook.rst
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@@ -0,0 +1,18 @@
cbook.is_sequence_of_strings recognizes string objects
``````````````````````````````````````````````````````

This is primarily how pandas stores a sequence of strings.

import pandas as pd
import matplotlib.cbook as cbook

a = np.array(['a', 'b', 'c'])
print(cbook.is_sequence_of_strings(a)) # True

a = np.array(['a', 'b', 'c'], dtype=object)
print(cbook.is_sequence_of_strings(a)) # True

s = pd.Series(['a', 'b', 'c'])
print(cbook.is_sequence_of_strings(s)) # True

Previously, the last two prints returned false.
8 changes: 6 additions & 2 deletions lib/matplotlib/cbook.py
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Expand Up @@ -783,8 +783,12 @@ def is_sequence_of_strings(obj):
"""
if not iterable(obj):
return False
if is_string_like(obj):
return False
if is_string_like(obj) and not isinstance(obj, np.ndarray):
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This will not catch new pd.Series as they are no longer ndarray sub-classes

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I think something like

if is_string_like(obj):
    # remove possible pandas
    obj_arr = np.asarray(obj)
    if not is_string_like(obj_arr):
        return False

or

if is_string_like(obj) and not isinstance(obj, np.ndarray):
    try:
        obj = s.values
    except AttributeError:
        # not pandas
        return False

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For reference

In [43]: isinstance(s, np.ndarray)
Out[43]: False

In [44]: type(s)
Out[44]: pandas.core.series.Series

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Thanks. I'll fix. I now see that Pandas has moved 3 major versions since I encountered this. I need to do a better job keeping all my virtual environments up-to-date.

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What does is_string_like(series of str) do? Does it loop through the array checking to see if each element is a str?

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is_string_like(obj) checks if string concatenation is possible. i.e If you can add a string to it, then it is "string like".

is_string_like(series of str) is indeed "string like".

Defn: is_string_like

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But we can not import pandas directly in core matplotlib for both technical
and policy reasons.

On Tue, Apr 28, 2015, 11:31 Phillip Cloud notifications@github.com wrote:

In lib/matplotlib/cbook.py
#4358 (comment):

@@ -783,8 +783,12 @@ def is_sequence_of_strings(obj):
"""
if not iterable(obj):
return False

  • if is_string_like(obj):
  •    return False
  • if is_string_like(obj) and not isinstance(obj, np.ndarray):

What does is_string_like(series of str) do? Does it loop through the
array checking to see if each element is a str?

—
Reply to this email directly or view it on GitHub
https://github.com/matplotlib/matplotlib/pull/4358/files#r29254616.

try:
obj = obj.values
except AttributeError:
# not pandas
return False
for o in obj:
if not is_string_like(o):
return False
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17 changes: 17 additions & 0 deletions lib/matplotlib/tests/test_cbook.py
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Expand Up @@ -26,6 +26,23 @@ def test_is_string_like():
assert cbook.is_string_like("hello world")
assert_equal(cbook.is_string_like(10), False)

y = ['a', 'b', 'c']
assert_equal(cbook.is_string_like(y), False)

y = np.array(y)
assert_equal(cbook.is_string_like(y), False)

y = np.array(y, dtype=object)
assert cbook.is_string_like(y)


def test_is_sequence_of_strings():
y = ['a', 'b', 'c']
assert cbook.is_sequence_of_strings(y)

y = np.array(y, dtype=object)
assert cbook.is_sequence_of_strings(y)


def test_restrict_dict():
d = {'foo': 'bar', 1: 2}
Expand Down