pandas 在python中将字符串转换为浮点数的问题
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Trouble converting string to float in python
提问by Minsky
I am fairly new to Python so forgive me this simple question. I'm trying to convert string to float. Here is a sample of the data:
我对 Python 相当陌生，所以请原谅我这个简单的问题。我正在尝试将字符串转换为浮点数。以下是数据示例：
0 10.65%
1 7.90%
When I try:
当我尝试：
df['int_rate'] = df['int_rate'].astype('float')
I get:
我得到：
ValueError: could not convert string to float: '13.75%'
When I try:
当我尝试：
df['int_rate'] = df['int_rate'].replace("%","", inplace=True)
And check my data, I get:
检查我的数据，我得到：
0 None
1 None
Any ideas what I'm doing wrong? Many thanks!
任何想法我做错了什么？非常感谢！
采纳答案by jezrael
You can use Series.replacewith parameter regex=Truefor replace substrings:
您可以使用Series.replacewith 参数regex=True来替换substrings：
df = pd.DataFrame({'int_rate':['10.65%','7.90%']})
df['int_rate'] = df['int_rate'].replace("%","", regex=True).astype(float)
print (df)
int_rate
0 10.65
1 7.90
df['int_rate'] = df['int_rate'].str.replace("%","")
print (df)
int_rate
0 10.65
1 7.90
2
df['int_rate'] = df['int_rate'].str.rstrip("%").astype(float)
print (df)
int_rate
0 10.65
1 7.90
See difference without it:
看到没有它的区别：
df = pd.DataFrame({'int_rate':['10.65%','7.90%', '%']})
df['int_rate_subs'] = df['int_rate'].replace("%","", regex=True)
df['int_rate_val'] = df['int_rate'].replace("%","")
print (df)
int_rate int_rate_subs int_rate_val
0 10.65% 10.65 10.65%
1 7.90% 7.90 7.90%
2 %
回答by Guillaume
As you guessed, ValueError: could not convert string to float: '13.75%'indicates that the %character blocks the convertion.
如您所料，ValueError: could not convert string to float: '13.75%'表示该%字符阻止了转换。
Now when you try to remove it:
现在，当您尝试删除它时：
df['int_rate'] = df['int_rate'].replace("%","", inplace=True)
You set inplace=Truein your replacement, which as the name suggests changes the dataframe in-place, so replace()method call returns None. Thus you store Nonein df['int_rate']and end up with a column containing only Nonevalues.
You should either do:
您设置inplace=True了替换，顾名思义，它会就地更改数据帧，因此replace()方法调用返回None. 因此，你存储None在df['int_rate']与仅包含一列最终None值。你应该这样做：
df['int_rate'] = df['int_rate'].replace("%","")
or
或者
df['int_rate'].replace("%","", inplace=True)
回答by Tyler
Since you're using a string, you could convert the value to a float using
由于您使用的是字符串，因此可以使用将值转换为浮点数
float(df['int_rate'][:-1])
This reads the string from the first position to the second to last position, 10.65 instead of 10.65%.
这将读取从第一个位置到第二个到最后一个位置的字符串，10.65 而不是 10.65%。
