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DOC GH22897 Fix docstring of join in pandas/core/frame.py #22904
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@@ -6440,6 +6440,8 @@ def append(self, other, ignore_index=False, | |
def join(self, other, on=None, how='left', lsuffix='', rsuffix='', | ||
sort=False): | ||
""" | ||
Append columns of another DataFrame. | ||
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Join columns with other DataFrame either on index or on a key | ||
column. Efficiently Join multiple DataFrame objects by index at once by | ||
passing a list. | ||
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@@ -6449,31 +6451,31 @@ def join(self, other, on=None, how='left', lsuffix='', rsuffix='', | |
other : DataFrame, Series with name field set, or list of DataFrame | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Do you mind removing the |
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Index should be similar to one of the columns in this one. If a | ||
Series is passed, its name attribute must be set, and that will be | ||
used as the column name in the resulting joined DataFrame | ||
used as the column name in the resulting joined DataFrame. | ||
on : name, tuple/list of names, or array-like | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. In the types, we try to have just the Python (or numpy...) types, and with a specific format that we can at some point parse and validate. Could you replace it by something like |
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Column or index level name(s) in the caller to join on the index | ||
in `other`, otherwise joins index-on-index. If multiple | ||
values given, the `other` DataFrame must have a MultiIndex. Can | ||
pass an array as the join key if it is not already contained in | ||
the calling DataFrame. Like an Excel VLOOKUP operation | ||
the calling DataFrame. Like an Excel VLOOKUP operation. | ||
how : {'left', 'right', 'outer', 'inner'}, default: 'left' | ||
How to handle the operation of the two objects. | ||
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* left: use calling frame's index (or column if on is specified) | ||
* right: use other frame's index | ||
* right: use other frame's index. | ||
* outer: form union of calling frame's index (or column if on is | ||
specified) with other frame's index, and sort it | ||
lexicographically | ||
specified) with other frame's index, and sort it. | ||
lexicographically. | ||
* inner: form intersection of calling frame's index (or column if | ||
on is specified) with other frame's index, preserving the order | ||
of the calling's one | ||
of the calling's one. | ||
lsuffix : string | ||
Suffix to use from left frame's overlapping columns | ||
Suffix to use from left frame's overlapping columns. | ||
rsuffix : string | ||
Suffix to use from right frame's overlapping columns | ||
Suffix to use from right frame's overlapping columns. | ||
sort : boolean, default False | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Can you replace the type |
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Order result DataFrame lexicographically by the join key. If False, | ||
the order of the join key depends on the join type (how keyword) | ||
the order of the join key depends on the join type (how keyword). | ||
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Notes | ||
----- | ||
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@@ -6485,70 +6487,67 @@ def join(self, other, on=None, how='left', lsuffix='', rsuffix='', | |
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Examples | ||
-------- | ||
>>> import pandas as pd | ||
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>>> caller = pd.DataFrame({'key': ['K0', 'K1', 'K2', 'K3', 'K4', 'K5'], | ||
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... 'A': ['A0', 'A1', 'A2', 'A3', 'A4', 'A5']}) | ||
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>>> caller | ||
A key | ||
0 A0 K0 | ||
1 A1 K1 | ||
2 A2 K2 | ||
3 A3 K3 | ||
4 A4 K4 | ||
5 A5 K5 | ||
key A | ||
0 K0 A0 | ||
1 K1 A1 | ||
2 K2 A2 | ||
3 K3 A3 | ||
4 K4 A4 | ||
5 K5 A5 | ||
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>>> other = pd.DataFrame({'key': ['K0', 'K1', 'K2'], | ||
... 'B': ['B0', 'B1', 'B2']}) | ||
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>>> other | ||
B key | ||
0 B0 K0 | ||
1 B1 K1 | ||
2 B2 K2 | ||
key B | ||
0 K0 B0 | ||
1 K1 B1 | ||
2 K2 B2 | ||
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Join DataFrames using their indexes. | ||
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>>> caller.join(other, lsuffix='_caller', rsuffix='_other') | ||
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>>> A key_caller B key_other | ||
0 A0 K0 B0 K0 | ||
1 A1 K1 B1 K1 | ||
2 A2 K2 B2 K2 | ||
3 A3 K3 NaN NaN | ||
4 A4 K4 NaN NaN | ||
5 A5 K5 NaN NaN | ||
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key_caller A key_other B | ||
0 K0 A0 K0 B0 | ||
1 K1 A1 K1 B1 | ||
2 K2 A2 K2 B2 | ||
3 K3 A3 NaN NaN | ||
4 K4 A4 NaN NaN | ||
5 K5 A5 NaN NaN | ||
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If we want to join using the key columns, we need to set key to be | ||
the index in both caller and other. The joined DataFrame will have | ||
key as its index. | ||
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>>> caller.set_index('key').join(other.set_index('key')) | ||
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>>> A B | ||
key | ||
K0 A0 B0 | ||
K1 A1 B1 | ||
K2 A2 B2 | ||
K3 A3 NaN | ||
K4 A4 NaN | ||
K5 A5 NaN | ||
A B | ||
key | ||
K0 A0 B0 | ||
K1 A1 B1 | ||
K2 A2 B2 | ||
K3 A3 NaN | ||
K4 A4 NaN | ||
K5 A5 NaN | ||
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Another option to join using the key columns is to use the on | ||
parameter. DataFrame.join always uses other's index but we can use any | ||
column in the caller. This method preserves the original caller's | ||
index in the result. | ||
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>>> caller.join(other.set_index('key'), on='key') | ||
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>>> A key B | ||
0 A0 K0 B0 | ||
1 A1 K1 B1 | ||
2 A2 K2 B2 | ||
3 A3 K3 NaN | ||
4 A4 K4 NaN | ||
5 A5 K5 NaN | ||
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key A B | ||
0 K0 A0 B0 | ||
1 K1 A1 B1 | ||
2 K2 A2 B2 | ||
3 K3 A3 NaN | ||
4 K4 A4 NaN | ||
5 K5 A5 NaN | ||
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See also | ||
-------- | ||
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Can you replace
append
byjoin
? I think in general they mean the same, but in this context may give the idea that the they are being added at the end of the DataFrame, or that they are not aligned.