在 Python 中将字符串转换为浮点数
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Convert string to float in Python
提问by JupiterOrange
I have a csv file and I am trying to plot some of the contents and need to convert the strings to floats. My problem is the following:
我有一个 csv 文件，我正在尝试绘制一些内容，需要将字符串转换为浮点数。我的问题如下：
When I run the code below,
当我运行下面的代码时，
with open('meteors.csv', 'rU') as csvfile:
reader=csv.reader(csvfile)
for row in reader:
print row[6]
I get this output:
我得到这个输出：
58.58333
When I instead try
当我尝试
print type(row[6])
I get this output:
我得到这个输出：
<type 'str'>
But when I try
但是当我尝试
print float(row[6])
I get this error:
我收到此错误：
ValueError: could not convert string to float: coordinate_1
Anyone know what's going on?
有谁知道这是怎么回事？
采纳答案by Burhan Khalid
Most likely you are seeing the first row, which has the column headers on your CSV file, and coordinate_1is a header.
您很可能会看到第一行，它在您的 CSV 文件中有列标题，并且coordinate_1是一个标题。
You can either skip the first row:
您可以跳过第一行：
with open('meteors.csv', 'rU') as csvfile:
reader=csv.reader(csvfile)
reader.next() # skips the first (header) row
for row in reader:
print row[6]
Or, use DictReader, like this:
或者，DictReader像这样使用：
with open('meteors.csv', 'rU') as csvfile:
reader=csv.DictReader(csvfile)
for row in reader:
print row['coordinate_1']
回答by Blender
Your CSV file probably has a header that lists the name of each column. You can't convert those names into floats, so that's where your error is coming from.
您的 CSV 文件可能有一个标题，其中列出了每列的名称。您无法将这些名称转换为floats，因此这就是您的错误的来源。
You have to consume the header first:
您必须首先使用标头：
with open('meteors.csv', 'rU') as csvfile:
reader = csv.reader(csvfile)
header = next(reader)
for row in reader:
print float(row[6])
