克服这一问题的最简单方法是强制每列使用正确的数据类型。如果从程序一开始就确保正确的数据类型，就不太可能出现这样的问题。

话虽如此，我在一段时间前创建了下面的代码，以准确地解决您面临的问题。定义每列正确的数据类型并在需要时转换为它，这并不是100%可靠的，但它可能会解决您的问题：

from __future__ import annotations

from collections import abc
from functools import wraps
from typing import (Any, TypeVar, Callable, Tuple, List, Hashable, Union,
                    Sequence, Collection)

import numpy as np
import pandas as pd
from numpy import dtype
from pandas._libs.tslibs import OutOfBoundsDatetime  # type: ignore
from pandas._libs.tslibs.timedeltas import array_to_timedelta64  # type: ignore

from pandas.core.dtypes.cast import sanitize_to_nanoseconds  # type: ignore
from pandas.core.dtypes.common import (  # type: ignore
    DT64NS_DTYPE,
    TD64NS_DTYPE,
    ensure_object,
    is_bool_dtype,
    is_complex_dtype,
    is_datetime64_dtype,
    is_datetime64tz_dtype,
    is_dtype_equal,
    is_float_dtype,
    is_integer_dtype,
    is_object_dtype,
    is_string_dtype,
    is_timedelta64_dtype,
)
from pandas.core.dtypes.dtypes import DatetimeTZDtype, ExtensionDtype
from pandas.core.dtypes.inference import is_list_like, iterable_not_string
from pandas.errors import IntCastingNaNError  # type: ignore
from pandas.util._exceptions import find_stack_level  # type: ignore
from pandas.errors import MergeError
from pandas.api.extensions import (
    register_dataframe_accessor,
    register_index_accessor,
    register_series_accessor
)
try:
    from pandas._typing import ArrayLike, DtypeObj  # type: ignore
except ImportError:
    DtypeObj = Union[np.dtype, "ExtensionDtype"]
    ArrayLike = Union["ExtensionArray", np.ndarray]  # type: ignore
try:
    from types import NoneType
except ImportError:
    NoneType = type(None)  # type: ignore

_int8_max = np.iinfo(np.int8).max
_int16_max = np.iinfo(np.int16).max
_int32_max = np.iinfo(np.int32).max
_int64_max = np.iinfo(np.int64).max

NumpyArrayT = TypeVar("NumpyArrayT", bound=np.ndarray)
IndexLabel = Union[Hashable, Sequence[Hashable]]
Axis = Union[str, int]
Axes = Collection[Any]
Shape = Tuple[int, ...]
Suffixes = Tuple[str, str]

def register_dataframe_method(method: Callable):
    """
    Register a function as a method attached to the ``Pandas DataFrame``.

    This is a wrapper for the ``pandas.core.accessor.AccessorProperty`` class.
  **It should be used as a decorator.**

    Parameters
    ----------
    method : callable
        The function to be registered.

    Example
    -------
    .. code-block:: python

        @register_dataframe_method
        def print_column(df, col):
            '''Print the dataframe column given'''
            print(df[col])
        df = pd.DataFrame({'col1': [1, 2, 3], 'col2': [4, 5, 6]})
        df.print_column('col1')
        # [1 2 3]
    ::

    See Also
    --------
    Official documentation of pandas accessors: 
    `https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.core
    .accessor.AccessorProperty.html>`_
    """

    def inner(*args,**kwargs):
        class AccessorMethod(object):
            def __init__(self, pandas_obj):
                self._obj = pandas_obj

            @wraps(method)
            def __call__(self, *args,**kwargs):
                return method(self._obj, *args,**kwargs)

        register_dataframe_accessor(method.__name__)(AccessorMethod)
        return method

    return inner()

def register_series_method(method: Callable):
    """Register a function as a method attached to the Pandas Series."""

    def inner(*args,**kwargs):
        class AccessorMethod(object):
            __doc__ = method.__doc__

            def __init__(self, pandas_obj):
                self._obj = pandas_obj

            @wraps(method)
            def __call__(self, *args,**kwargs):
                return method(self._obj, *args,**kwargs)

        register_series_accessor(method.__name__)(AccessorMethod)
        return method

    return inner()

def register_index_method(method: Callable):
    """Register a function as a method attached to the Pandas Index."""

    def inner(*args,**kwargs):
        class AccessorMethod(object):
            __doc__ = method.__doc__

            def __init__(self, pandas_obj):
                self._obj = pandas_obj

            @wraps(method)
            def __call__(self, *args,**kwargs):
                return method(self._obj, *args,**kwargs)

        register_index_accessor(method.__name__)(AccessorMethod)
        return method

    return inner()

def find_common_type(
        types: List[DtypeObj]) -> dtype | dtype | ExtensionDtype | object | Any:
    """Find a common data type among the given dtypes.

    Parameters
    ----------
    types : list[DtypeObj]
        A list of possible dtypes that can be considered for conversion.

    Returns
    -------
    dtype | dtype | ExtensionDtype | object | Any
        pandas extension or numpy dtype.

    Raises
    ------
    ValueError
        Raises ValueError if :param:`types` is empty.

    See Also
    --------
    The function `numpy.find_common_type <numpy.find_common_type>`_
    contains the numpy implementation of this function behavior.
    """
    if not types:
        raise ValueError("No types given.")

    first = types[0]

    # Workaround for find_common_type([np.dtype('datetime64[ns]')] * 2) => 
    # object
    if all(is_dtype_equal(first, t) for t in types[1:]):
        return first

    # Get unique types (dict.fromkeys is used as order-preserving set())
    types = list(dict.fromkeys(types).keys())

    if any(isinstance(t, ExtensionDtype) for t in types):
        for _type in types:
            if isinstance(_type, ExtensionDtype):
                res = _type._get_common_dtype(types)
                if res is not None:
                    return res
        return np.dtype("object")

    # Take the lowest unit
    if all(is_datetime64_dtype(t) for t in types):
        return np.dtype("datetime64[ns]")
    if all(is_timedelta64_dtype(t) for t in types):
        return np.dtype("timedelta64[ns]")

    # Don't mix bool, int, float or complex
    # this is different from what numpy does, when it casts bools represented
    # by floats or ints to int
    has_bools = any(is_bool_dtype(t) for t in types)

    if has_bools:
        for t in types:
            if is_integer_dtype(t) or is_float_dtype(t) or is_complex_dtype(t):
                return np.dtype("object")

    return np.find_common_type(types, [])

def normalize_dtypes(xdf: pd.DataFrame, ydf: pd.DataFrame) -> tuple[pd.DataFrame, pd.DataFrame]:
    """
    Normalize the underlying column dtypes of two input dataframes.

    Function determines which columns exist on both dataframes, and only
    converts those ``pd.Series`` of values to the same dtype.
    :func:`find_common_type` finds the common data type supported to column
    on both input dataframes.

    Parameters
    ----------
    xdf : pd.DataFrame
        The first dataframe to be updated.
    ydf : pd.DataFrame
        The second dataframe.

    Returns
    -------
    tuple[pd.DataFrame, pd.DataFrame]
        The two dataframes with the same data types.
    """
    return _normalize_dtypes(xdf, ydf, [*xdf.columns, *ydf.columns])

def _normalize_dtypes(xdf: pd.DataFrame, ydf: pd.DataFrame,
                      use_cols: abc.Iterable) -> tuple[
    pd.DataFrame, pd.DataFrame]:
    """
    Normalize the underlying column dtypes of the given dataframes.

    Function finds columns in common (by column name), using each
    dataframe's columns and the user-provided list of columns to normalize
    data type. This dispatch won't normalize the data types of all the columns
    with matching names.

    Parameters
    ----------
    xdf : pd.DataFrame
        The first dataframe to be updated.
    ydf : pd.DataFrame
        The second dataframe.
    use_cols : abc.Iterable
        User-defined list of column names to normalize.

    Returns
    -------
    tuple[pd.DataFrame, pd.DataFrame]
        The two dataframes with the same data types.

    .. versionchanged:: 1.0.3

       Columns that are converted to string, now have any trailing '.0' removed.
    """
    int_dtypes = ['int8', 'int16', 'int32', 'int64', 'uint8', 'uint16',
                  'uint32', 'uint64']
    float_dtypes = ['float16', 'float32', 'float64']
    bool_dtypes = ['bool']
    object_dtypes = ['object']
    datetime_dtypes = ['datetime64[ns]', 'datetime64[tz]', 'datetime64']
    string_dtypes = ['string', 'str']

    if not iterable_not_string(use_cols):
        use_cols = [use_cols]

    cols_to_consider = list(set(xdf.columns) & set(use_cols) & set(ydf.columns))

    astype_dict = {}
    for col in cols_to_consider:
        xdtype = xdf[col].dtype
        ydtype = ydf[col].dtype
        common_type = find_common_type([xdf[col].dtype, ydf[col].dtype])
        if common_type == object:
            for dtyp in [xdtype, ydtype]:
                if dtyp in [*int_dtypes, *float_dtypes]:
                    common_type = 'float64'
            if common_type == 'float64':
                try:
                    xdf[col].astype(common_type)
                    ydf[col].astype(common_type)
                except ValueError:
                    common_type = 'str'

        astype_dict[col] = str if common_type == object else common_type
    xdf, ydf = xdf.astype(astype_dict), ydf.astype(astype_dict)
    str_cols = [k for k, v in astype_dict.items() if v in string_dtypes]

    for col in str_cols:
        xdf[col] = xdf[col].str.replace('.0', '')
        ydf[col] = ydf[col].str.replace('.0', '')
    return xdf, ydf

def maybe_make_list(obj: Any) -> Any | list[Any]:
    """
    Convert ``obj`` to ``list``, if ``obj`` is ``Iterable``,
    and more specifically a ``string``.
    Function works similarly to :func:`iterable_not_string`, but instead of
    returning True or False, it returns the object as a list, whenever it is
    possible.

    Parameters
    ----------
    obj : Any
        The object to be evaluated and possibly converted to list.

    Returns
    -------
    Any | list[Any]
        The original object, or a list of the original object.

    Examples
    --------
    >>> x = '12345'
    >>> list(x)
    ['1', '2', '3', '4', '5']
    >>> maybe_make_list(x)
    ['12345']
    >>> maybe_make_list(None)
    >>> maybe_make_list(['1', '2', '3'])
    ['1', '2', '3']
    """
    if obj is not None and not isinstance(obj, (tuple, list)):
        return [obj]
    return obj

@register_dataframe_method
def safe_merge(
    left: pd.DataFrame,
    right: Union["DataFrame", "Series"],
    how: str = "inner",
    on: IndexLabel | None = None,
    left_on: IndexLabel | None = None,
    right_on: IndexLabel | None = None,
    left_index: bool = False,
    right_index: bool = False,
    sort: bool = False,
    suffixes: Suffixes = ("_x", "_y"),
    copy: bool = True,
    indicator: bool = False,
    validate: str | None = None,
    allow_inflation: bool = True,
) -> pd.DataFrame:
    """Merge two DataFrames, making sure merge keys have the same data type.

    Parameters
    ----------
    left : pd.DataFrame
    right : Union["DataFrame", "Series"]
    how : str {‘left’, ‘right’, ‘outer’, ‘inner’, ‘cross’}, default ‘inner’
        The type of merge to be performed.
        * 'left': use only keys from the left frame, like an SQL left
          outer join; preserve key order.
        * 'right': use only keys from right frame, like an SQL right
          outer join; preserve key order.
        * 'outer': use union of keys from both frames, like an SQL
          full outer join; sort keys lexicographically.
        * 'inner': use intersection of keys from both frames, like an
          SQL inner join; preserve the order of the left keys.
        * 'cross': creates the cartesian product from both frames,
          preserves the order of the left keys.
    on : IndexLabel | None, default None
        Column or index level names to join on. These must be found in both
        DataFrames. If on is None and not merging on indexes then this defaults
        to the intersection of the columns in both DataFrames.
    left_on : IndexLabel | None, default None
        Column or index level names to join on in the left DataFrame. Can also
        be an array or list of arrays of the length of the left DataFrame.
        These arrays are treated as if they are columns.
    right_on : IndexLabel | None = None
        Column or index level names to join on in the right DataFrame. Can
        also be an array or list of arrays of the length of the right
        DataFrame. These arrays are treated as if they are columns.
    left_index : bool, default False
        Use the index from the left DataFrame as the join key(s). If it is a
        MultiIndex, the amount of keys in the other DataFrame (either the
        index or several columns) must match the amount of levels.
    right_index : bool, default False
        Use the index from the right DataFrame as the join key. Same caveats
        as left_index
    sort : bool, default False
        Sort the join keys lexicographically in the result DataFrame. If
        False, the order of the join keys depends on the join type (how
        keyword)
    suffixes : Suffixes, default is (“_x”, “_y”)
        A length-2 sequence where each element is optionally a string
        indicating the suffix to add to overlapping column names in left and
        right respectively. Pass a value of None instead of a string to
        indicate that the column name from left or right should be left
        as-is, with no suffix. At least one of the values must not be None
    copy : bool, default True
        If False, avoid copy if possible
    indicator : bool | str, default False
        If True, adds a column to the output DataFrame called “_merge” with
        information on the source of each row. The column can be given a
        different name by providing a string argument. The column will have a
        Categorical type with the value of “left_only” for observations whose
        merge key only appears in the left DataFrame, “right_only” for
        observations whose merge key only appears in the right DataFrame,
        and “both” if the observation's merge key is found in both DataFrames
    validate : str | None, optional
        If specified, checks if merge is of specified type.
        * "one_to_one" or "1:1": check if merge keys are unique in both
          left and right datasets.
        * "one_to_many" or "1:m": check if merge keys are unique in the
          left dataset.
        * "many_to_one" or "m:1": check if merge keys are unique in right
          dataset.
        * "many_to_many" or "m:m": allowed, but does not result in checks.
    allow_inflation : bool, default False
        If “False”, allows for merge to duplicates rows. Otherwise,
        drops duplicates after the following rules:
        * If how == "left": drop duplicate keys from :param:`right`
          dataframe.
        * If how == "right": drop duplicate keys from :param:`left`
          dataframe.

    Returns
    -------
    pd.DataFrame
        A DataFrame of the two merged objects.

    Raises
    ------
    MergeError
        * If :param:`on` and :param:`left_on` or :param:`right_on` are defined.
        * If :param:`on` and :param:`left_index`, :param:`right_index` defined.
        * If :param:`left_on` and :param:`right_index` are defined,
          or :param:`right_on` and :param:`left_index` are defined.
    ValueError
        * If :param:`left_on` and :param:`right_on` are defined, but both
          attributes do not contain the same amount of columns.

    Examples
    --------
    >>> df1 = pd.DataFrame({'A': ['A0', 'A1', 'A2'], 'B': [20, 30, 40]})
    >>> df2 = pd.DataFrame({'a': ['A0', 'A1', 'A3'], 'b': [20, 50, 40]})
    >>> df1.safe_merge(df2, left_on=['A', 'B'], right_on=['a', 'b'],
    ... how='inner')
        A   B   a   b
    0   A0  20  A0  20
    >>> df2 = pd.DataFrame({'a': ['A0', 'A1', 'A3'], 'b': ['20', '50', '40']})
    >>> df1.merge(
    ... df2, left_on=['A', 'B'], right_on=['a', 'b'], how='inner'
    ... ) #  doctest: +ELLIPSIS
    Traceback (most recent call last):
    ...
    ValueError: You are trying to merge on int64 and object columns...
    >>> df1 = pd.DataFrame({'a': ['A0', 'A1', 'A2'], 'b': [20, 30, 30]})
    >>> df2 = pd.DataFrame({'A': ['A0', 'A1', 'A3'], 'B': ['20', '30', '40']})
    >>> df1.safe_merge(df2, left_on=['a', 'b'], right_on=['A', 'B'],
    ... how='inner')
        a   b   A   B
    0   A0  20  A0  20
    1   A1  30  A1  30
    """
    if on is not None:
        on = maybe_make_list(on)
        if any([left_on, right_on]):
            MergeError(
                'Can only pass argument "on" OR "left_on" and "right_on", '
                '' "not a combination of both.")
        left_on = right_on = on

    if left_on is not None and right_on is not None:
        left_on, right_on = maybe_make_list(left_on), maybe_make_list(right_on)
        if len(left_on) != len(right_on):
            raise ValueError("len(right_on) must equal len(left_on)")
        if any([left_index, right_index]):
            raise MergeError(
                'Can only pass argument "left_on" and "right_on"'
                ' OR "left_index" and "right_index", not a combination of both.'
            )
        right = right.rename(columns=dict(zip(right_on, left_on)))
        left, right = normalize_dtypes(left, right)

        right = right.rename(columns=dict(zip(left_on, right_on)))
        if not validate and not allow_inflation:
            validate = get_validation_relationship(how)

        if validate:
            left, right = eval_validation(left, right, left_on, right_on,
                                          validate)

        return left.merge(
            right,
            how=how,  # type: ignore
            left_on=left_on,
            right_on=right_on,
            sort=sort,
            suffixes=suffixes,
            copy=copy,
            indicator=indicator,
            validate=validate,  # type: ignore
        )

    if all([left_index, right_index]):
        return left.merge(
            right,
            how=how,  # type: ignore
            left_index=left_index,
            right_index=right_index,
            sort=sort,
            suffixes=suffixes,
            copy=copy,
            indicator=indicator,
            validate=validate,  # type: ignore
        )
    raise ValueError("Unsupported argument combination")

def get_validation_relationship(how: str) -> str:
    """Return the validation relationship for the given :param:`how`.

    Parameters
    ----------
    how : str {'inner', 'left', 'right'}
        The merge method, being used.

    Returns
    -------
    str
        The validation relationship to be used. Available options are:

        * 'many_to_one' : when :param:`how` is 'left'
        * 'one_to_many' : when :param:`how` is 'right'
        * 'one_to_one' : when :param:`how` is 'inner'

    Raises
    ------
    ValueError
        If :param:`how` is not one of 'inner', 'left', 'right'.
    MergeError
        If :param:`how` is 'left' or 'right' and the validation relationship
        is 'one_to_many' or 'many_to_one'.

    Notes
    -----
    This function does not support 'outer' as a valid :param:`how` value.
    However, the method ``pd.DataFrame.merge`` does support 'outer' as a valid
    :param:`how` value (but there aren't many usages on the project's source
    code).
    """
    if how == "left":
        return "many_to_one"
    if how == "right":
        return "one_to_many"
    if how == "inner":
        return "one_to_one"
    raise ValueError(f'Unsupported "how" argument {how}')

def eval_validation(
    left: pd.DataFrame,
    right: pd.DataFrame,
    left_on: IndexLabel,
    right_on: IndexLabel,
    validate: str,
):
    """
    Evaluate the validation relationship between `left` and `right`, ensuring
    that the `left` and `right` `dataframes` are compatible with the validation
    strategy.

    Use :func:`get_validation_relationship` to get the validation relationship,
    based on the type of merger being performed.

    Parameters
    ----------
    left : pd.DataFrame
        Left dataframe
    right : pd.DataFrame
        Right dataframe
    left_on : IndexLabel
        Left index label
    right_on : IndexLabel
        Right index label
    validate : str {'one_to_one', 'one_to_many', 'many_to_one'}
        Validation strategy.

    Returns
    -------
    tuple[pd.DataFrame, pd.DataFrame]
        Left and right dataframes after validation.

    Raises
    ------
    ValueError
        If the validation strategy is not supported.

    Notes
    -----
    The function ``map``, can be used to apply functions to ``Iterables``.
    ``Iterables`` are objects that have a ``__len__`` attribute. These include,
    for example, lists, tuples, strings, bytes, and bytearrays. You can also
    define your own iterables classes, by defining the ``__len__`` attribute.
    """
    if validate == "many_to_one":
        right = right.drop_dup_and_log(subset=right_on)
    elif validate == "one_to_many":
        left = left.drop_dup_and_log(subset=left_on)
    elif validate == "one_to_one":
        # map can be used to apply functions to an iterable (e.g. list)
        left, right = map(
            lambda args: args[0].drop_duplicates(subset=args[1]),
            tuple(zip([left, right], [left_on, right_on])),
        )
    else:
        raise ValueError(f'Unsupported "validate" argument {validate}')
    return left, right

# == Example ======================

df1 = pd.DataFrame({'A': ['A0', 'A1', 'A2'], 'B': [20, 30, 40]})
df2 = pd.DataFrame({'a': ['A0', 'A1', 'A3'], 'b': ['20', '50', '40']})
df1.safe_merge(df2, left_on=['A', 'B'], right_on=['a', 'b'], how='inner')

# Prints:

# A     B   a     b

# 0  A0  20.0  A0  20.0

# Using normal "merge" operation":

df1.merge(df2, left_on=['A', 'B'], right_on=['a', 'b'], how='inner')

# ...

# ValueError: You are trying to merge on int64 and object columns. If you wish to proceed you should use pd.concat

示例

上面的代码定义了一个名为safe_merge的自定义Pandas Dataframe 方法，您可以使用与普通pandas.DataFrame.merge方法相同的方式(事实上，它使用了实际pandas.DataFrame.merge源代码的大约80%)。

下面是一个它能做什么的例子：

df1 = pd.DataFrame({'A': ['A0', 'A1', 'A2'], 'B': [20, 30, 40]})
df2 = pd.DataFrame({'a': ['A0', 'A1', 'A3'], 'b': ['20', '50', '40']})
df1.safe_merge(df2, left_on=['A', 'B'], right_on=['a', 'b'], how='inner')

# Prints:

# A     B   a     b

# 0  A0  20.0  A0  20.0

下面是使用普通pandas.DataFrame.merge的相同示例：

# Using normal "merge" operation":

# df1.merge(df2, left_on=['A', 'B'], right_on=['a', 'b'], how='inner')

# ...

# ValueError: You are trying to merge on int64 and object columns. If you wish to proceed you should use pd.concat