string = 'cool' df = pd.DataFrame(columns=['string_values']) Append
df.append(string) I get this error when I try to append it into df. (Is it only for numerical data?)
cannot concatenate object of type "<class 'str'>"; only pd.Series, pd.DataFrame, and pd.Panel (deprecated) objs are valid I just want to add a string value string = 'cool' into the dataframe, but I get this error.
2 Answers
I think best is use DataFrame contructor and assign one element list:
string = 'cool' df = pd.DataFrame([string], columns=['string_values']) print (df) string_values 0 cool If strings are generated in loop best is append them to one list and then pass to constructor only once:
L = [] for x in range(3): L.append(string) df = pd.DataFrame(L, columns=['string_values']) print (df) string_values 0 cool 1 cool 2 cool Performance:
In [43]: %%timeit ...: L = [] ...: for x in range(1000): ...: value1 = "dog" + str(x) ...: L.append(value1) ...: ...: df = pd.DataFrame(L, columns=['string_values']) ...: 1.29 ms ± 56.6 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each) In [44]: %%timeit ...: df = pd.DataFrame(columns=['string_values']) ...: for x in range(1000): ...: value1 = "dog" + str(x) ...: df = df.append({'string_values': value1}, ignore_index=True) ...: 1.19 s ± 34.3 ms per loop (mean ± std. dev. of 7 runs, 1 loop each) If you need to add more than a single value, see @jezraels answer. If you only need to add a single value, you can do this:
import pandas as pd df = pd.DataFrame(columns=['string_values']) value1 = "dog" df = df.append({'string_values': value1}, ignore_index=True) # string_values # 0 dog value2 = "cat" df = df.append({'string_values': value2}, ignore_index=True) # string_values # 0 dog # 1 cat Check the docs.
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