Matplotlib can't suppress figure window

Question

I'm having trouble with matplotlib insisting on displaying a figure wnidow even when I haven't called show().

The function in question is:

def make_plot(df):
    fig, axes = plt.subplots(3, 1, figsize=(10, 6), sharex=True)
    plt.subplots_adjust(hspace=0.2)

    axes[0].plot(df["Date_Time"], df["T1"], df["Date_Time"], df["T2"])
    axes[0].set_ylabel("Temperature (C)")
    axes[0].legend(["T1", "T2"], bbox_to_anchor=(1.12, 1.1))
    axes[1].semilogy(df["Date_Time"], df["IGP"], df["Date_Time"], df["IPP"])
    axes[1].legend(["IGP", "IPP"], bbox_to_anchor=(1.12, 1.1))
    axes[1].set_ylabel("Pressure (mBar)")
    axes[2].plot(df["Date_Time"], df["Voltage"], "k")
    axes[2].set_ylabel("Voltage (V)")
    current_axes = axes[2].twinx()
    current_axes.plot(df["Date_Time"], df["Current"], "r")
    current_axes.set_ylabel("Current (mA)")
    axes[2].legend(["V"], bbox_to_anchor=(1.15, 1.1))
    current_axes.legend(["I"], bbox_to_anchor=(1.14, 0.9))

    plt.savefig("static/data.png")

where df is a dataframe created using pandas. This is supposed to be in the background of a web server, so all I want is for this function to drop the file in the directory specified. However, when it executes it does this, and then pulls up a figure window and gets stuck in a loop, preventing me from reloading the page. Am I missing something obvious?

EDIT: Forgot to add, I am running python 2.7 on Windows 7, 64 bit.

Solution

Perhaps just clear the axis, for example:

plt.savefig("static/data.png")
plt.close()

will not plot the output in inline mode. I can't work out if is really clearing the data though.